UC-NRLF 


B   M   MOD   M71 


ARY 


THE  LIBRARY 

OF 

THE  UNIVERSITY 

OF  CALIFORNIA 


GIFT  OF 


Abraham  livinston,  O.D, 


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POCKET 
Ophthalmic    Dictionary 

INCLUDING 

Pronunciation,    Derivation    and  Definition 
OF  THE  WORDS 

USED  IN 

Optometry  and  Ophthalmology 


Together  with  a  complete  descrip- 
tion of  the  light  wave  theory, 
Anatomy  of  the  Eye,  functions, 
blood  and  nerve  supply  of  the  dif- 
ferent parts,  lietinoscope,  Oph- 
thalmoscope, Trial  Case  and  how 
to  use  them.  Rules,  Transposi- 
tion, Toric  and  other  lenses. 
State  board  questions. 


By  JAMES  J.  LEWIS,  Oph.  D. 

rrofessor  of   Optometry   in   the  Nortluru    Illinois   Col- 
lege of  Ophthalmology  and  Otology,  Chicago. 


FIFTH  EDITION 
Revised  and  Enlarged  Illustrated 


Copyright,  1908,  1910,  1913,  1916,  J.  J.  LEWIS 

\ 


'z.u 


To   the  Profession: 

This  edition  has  been  compiled  with  a  great 
deal  of  care.  Realizing  that  perfection  in  its 
full  sense  has  never  been  attained  by  mortal  man, 
the  author  invites  the  unbiased  and  conscientious 
criticism  of  the  readers  and  users  of  this  Dictionary 
and  hereby  earnestly  solicits  the  same  to  the  end 
that  the  future  editions  may  profit  by  the  honest 
convictions  of  studious  oculists,  physicians  and 
optometrists. 

I  cannot  conclude  without  expressing  my  deep 
sense  of  obligation  to  the  profession  for  their  kind 
reception  of  this  work.  Feeling  the  responsibility 
incurred  by  those  who  attempt  to  teach  others,  I 
have  spared  no  amount  of  labor  or  cost  to  render 
this  volume  clear,  practical  and  useful. 
Very  respectfully, 

THE  AUTHOR. 


GIFT 


PREFACE 

TO   THE   FIFTH   EDITION 


THE  very  favorable  reception  accorded  (he 
fourth  edition  of  this  work  has  encourajjed 
the  author  to  still  further  revise  it,  incorporating 
in  its  pages  a  considerable  number  of  new  defini- 
tions, as  well  as  giving  an  accurate  and  complete 
derivation  of  all  the  technical  terms  used  in 
Optical  nomenclature,  making  the  book  of  the 
highest  value  to  the  practitioner  and  student 
alike. 

In  presenting  this  fifth  edition  of  the  Lewis 
Dictionary  and  Encyclopedia,  I  wish  to  express 
my  appreciation  for  the  invaluable  assistance 
extended  by 

J.  B.  McFATRICH.  M.  S..  M.  D., 

Professor  of  the  Principles  of  Ophthalmology  and  Oto'ogv. 

GEO.    WILBUR    McFATRICH,    M.    D., 

Professor    of    Clinical    and    Didactic    Ophthalmology    and 

Otology. 

HENRY  S.  TUCKER,  A.  M.,  M.  D., 

Professor    of    Anatomy    and    Physiology    of    the    Eye    aiil 

Brain. 

E.  G.  TROWBRIDGE,  M.  D., 

Professor   of   Dioptrics. 

J.  3.  L. 

660 


Abbreviations  and  Optical  Signs 

Ace Accommodation. 

Aet Age. 

Am Ametropia. 

An Anisometropia. 

As Astigmatism, 

Asth Asthenopia. 

Ax Axis. 

Cc.  or  —  ( minus ) Concave. 

Ce Centigrade. 

Cm Centimeter. 

Cx.  or  +  (plus) Convex. 

Cyl Cylinder. 

D. Dioptry, 

D.  Cc Double  concave. 

D.  Cx Double  convex. 

D.  T Distance  test. 

E.  or  Em Emmetropia. 

e.  g For  example. 

H.  or  Hy Hypermetropia. 

In Inches. 

L.  or  J..  E Left  eye. 

M.  or  My Myopia. 

Mm Millimeter. 

N Nasal. 

Nv Naked  vision. 

O.  D.  (Oculus  Dexter) ....  Right  eye. 
O.  S.  (Oculus  Sinister) .  .  .  Left  eye. 

O.  U.  (Oculi  Unati) Both  eyes. 

P.  or  Pb Presbyopia. 

P.  Cc Periscopic  concavC: 

P.  Cx '. Periscopic  convex. 


ADDrevialions  ana  uptical  ;!)igns — L.on. 

P.  D Inter-Pupillary  distance. 

PI : Piano. 

p.  p.  (Punctum 

Proximum) Near  point. 

p.  r.  (Punctum 

Remotum) Far  point. 

Pr Prism. 

R.  or  R.  E Right  eye. 

R.  T Reading  test. 

Rx Prescription. 

Sb Strabismus. 

S.  or  Sph Spherical. 

T Temporal. 

Ty Type. 

V Vision. 

Ya Visual  acuteness. 

W.  P Working  point. 

-r Plus  convex. 

— Minus  —  concave. 

C  • Combined  with. 

° Degree. 

A Prism  Dioptry. 

= Equal  to. 

x Infinity,  20  ft.  or  farther. 

" Line,  12th  part  of  inch. 

± Plus  or  (and)  minus. 

V Centrad. 

X Multiplied  by;  times. 

-^ Divided  by. 

> Is  (or  are)  greater  than. 

< Is  (or  are)  less  than. 


Lewis  Ophthalmic  Dictionary 


/iL  (Gr.  alpha,  privative.)  A  prefix  convejing  a 
negative  meaning;  as  without,  away,  not,  from. 

Abaxial  (ab-aks'-e-al).  Not  situated  in  the  line  of 
the  axis. 

Abbe,  Prof.  Ernst.  A  German  professor  and  in- 
ventor of  an  apparatus  for  measuring  the  in- 
dices of  refraction.     1845-1905. 

Abducens  (ab-du'-senz).  (L.  ab.  =  from  +  ducere 
=  to  draw.)  The  external  rectus  muscle,  whose 
action  it  is  to  rotate  the  eye  outward.  It  arises 
by  two  heads,  one  from  the  lower  margin  of  the 
sphenoidal  fissure;  the  other  from  the  outer 
margin  of  the  optic  foramen.  Its  tendon  is  in- 
serted into  the  sclera  8  mm.  from  the  outer 
margin  of  the  cornea.  Under  normal  conditions 
these  muscles  should  overcome  about  8  degrees 
of  prism,  base  in.  It  is  controlled  by  the  sixth 
pair  of  cranial  nerves  (abducens). 

Abducent  (ab-du'-sent).  Abducting;  drawing  from 
the  center. 

Abduct  (ab  =  away,  ducere  =  to  lead).  To  draw 
away  from  the  median  line. 

Abduction  (ab-duc'-shun).  The  act  of  turning  the 
eye  outward  from  its  position  of  rest.  For  test- 
ing the  power  of  the  abductors  or  external  recti 
muscles,  use  the  strongest  prism,  base  in,  with 
which  the  eyes  can  overcome  diplopia,  looking 
20  feet  away,  and  deduct  any  imbalance. 


S  LEWIS  POCKET 

Abductor  (ab-duc'-tor).  Any  muscle  that  abducts. 
For  instance,  abductor  oculi.  the  external  rectus 
muscle. 

Aberration  (ab-er-a'-shun).  (L.  ab  =  away,  errare 
=  to  wander.)  Wandering  from  normal.  When 
applied  to  lenses  would  mean,  unable  to  obtain 
a  perfect  focus.  It  is  due  to  the  greater  refrac- 
tive power  of  the  edge  over  the  center  of  convex 
lenses,  thus  causing  the  image  to  be  somewhat 
blurred.  In  the  eye  the  iris  shuts  off  the  edge  of 
the  lens,  and  in  this  way  prevents  spherical 
aberration.  Chromatic  Aberration,  dispersion  of 
colors.  Owing  to  the  colored  rays  having  differ- 
ent degrees  of  refractibility  they  are  not  focused 
at  the  same  distance. 

Ablatio-retinae  (ab-la'-she-o-ret'-in-e).  (L.  ab  = 
away  -f  latum  =  to  take.)  Detachment  of  the 
retina. 

Ablepharia  (ah-blef-ar'-e-ah).  (Gr.  a  =  not + 
blepharon  =  eyelid.)  That  condition  in  which 
the  eyelids  are  absent.    Also,  Ablepharous. 

Ablepsia  (ah-blep'-se-ah).  (Gr.  a  =  not  +  blepo  ^ 
I  see.)    Blindness — want  of  sight. 

Abnormal  (L.  ab  =  away  +  normal  =  ?ule).  Away 
from  normal.  Relating  to  vision  would  mean, 
any  defect  of  sight.  (Ametropia.)  An  eye 
wherein  parallel  rays  of  light  do  not  focus  on 
the  retina  with  the  muscles  of  accommodation 
at  rest. 

Abrasio-cornea    (ab-ra'-si-o-cor'-ne-ah).      (L.    ab  - 
away  +  radere  =  to  scrape.)    The  rubbing  off  of 
the  outer  layer  of  the  cornea. 

Abscess    (ab'-ses).     (L.    ab  —  away  +  cedere  =  to 


OPHTHALMIC  DICTIONARY  9 

depart.)     A    collection    of    pus    in    any    cavity 
formed  by  the  separation  of  tissue. 

Abscissa  (ab-sis'-a).  (L.  cut  off.)  A  certain  line 
used  in  determining  the  position  of  a  point  in  a 
plane. 

Absorption  (ab-sorp'-shun).  (L.  ab,  and  sorbere  = 
to  suck  in.)  A  term  applied  in  the  operation  for 
cataract  where  the  lens  capsule  is  needled, 
allowing  the  aqueous  humor  to  absorb  the  lens. 

Absorptive.  Anything  that  has  the  power  of  ab- 
sorption. 

Abstract  (ab'-strakt).  (L.  abstractus  =  drawn 
away.)  An  abstract  number  is  a  number  not 
designated  as  referring  to  any  particular  class 
of  objects. 

Acceleration.  An  increase  in  rapidity;  opposed  to 
retardation. 

Accommodation  (ak-kom'-mo-da'-shun).  (L.  ac- 
commodare  =  to  depart.)  The  act  of  adjusting 
the  eye  to  see  within  its  far  point  of  vision. 
Optical  adjustment.  It  takes  place  by  contract- 
ing the  ciliary  muscles  which  encircle  the  crys- 
talline lens  and  draws  forward  the  inner  layer 
of  the  choroid  and  hyaloid  membrane,  the  sus- 
.pensory  ligaments  becoming  relaxed,  and  the 
lens  (by  its  own  elasticity)  allowed  to  assume 
a  greater  convexity,  especially  its  anterior  sur- 
face, thus  increasing  its  refraction.  It  is  never 
used  unless  the  light  attempts  to  focus  behind 
the  retina.  Amplitude  of  Accommodation  is  the 
difference  in  the  dioptric  power  of  the  eye  when 
in  a  state  of  complete  relaxation  and  when  the 
full  amount  of  accommodation  is  in  use;  or.  in 
other  words,  the  amount  of  accommodation  an 


10  LEWIS  POCKET 

eye  possesses.   Amplitude  of  Accommodation  at 
different  ages  (from  Landolt)  as  follows: 

Age  in  Amplitude 

Years  (dioptrics) 

10 14 

15 12 

20 10 

25 8.5 

30 7.0 

35 5.5 

40 4.5 

45 3.5 

50 2.0 

55 1.75 

60 1.0 

65 0.75 

70 0.0 

This  is  approximately  correct,  but  individuals 
differ  in  the  amount  of  accommodation  they 
possess  at  the  same  age.  Accommodation  is 
spoken  of  as  binocular,  absolute,  and  relative. 

Binocular  Accommodation  is  the  full  amount 
of  accommodation  which  both  eyes  can  use 
together  while  converging. 

Absolute  Accommodation  is  the  total  amount 
of  accommodation  of  one  eye  only,  the  other 
being  covered. 

Relative  Accommodation  is  the  amount  of 
accommodation  that  can  be  used  without  chang- 
ing the  convergence;  that  is,  by  lenses  or  other 
means. 

Spasm  of  Accommodation,  the  inability  on 
the  part  of  the  patient  to  relax  his  accommoda- 
tion without  drugs. 


OPHTHALMIC  DICTIOXAltV  11 

Center  of  Accommodation  is  situated  beneath 
the  floor  of  the  aqueduct  of  Silvius. 

Paralysis  of  Accommodation  is  the  loss  of 
power  of  movement  in  the  ciliary  muscles 
through  injury,  disease,  or  a  drug  affecting  the 
nerve  supply. 

Negative  Accommodation  would  mean  that 
the  eye  possesses  the  ability  to  decrease  its 
dioptric  power  from  that  which  it  possesses  in 
a  state  of  rest.  By  so  doing  would  lengthen  its 
principal  focus. 

Accommodation  is  interfered  with  by  harden- 
ing of  the  lens,  weakness  of  the  ciliary  muscles, 
paralysis  of  the  third  nerve,  loss  of  the  crystal- 
line lens,  or  use  of  drugs,  such  as  Atropine. 

Achloropsia  (Gr.  a  =  without  -{-  chloros  =  green 
-f- opsis  =  vision).  Green-blindness,  color  blind- 
ness as  regards  green. 

Achroma  (ak-ro'-mah).  (Gr.  a  =  not  +  chroma  = 
color.)    Without  color. 

Achromatic  Lens  (ah-kro-mat'-ik).    (See  Lens.) 

Achromatism  (ah-kro'-ma-tism).  Absence  of  chro- 
matic aberration. 

Achromatistous  (ah-kro-mat-is'-tus).  Deficient  in 
coloring  matter  or  pigment. 

Achromatopsia  (ah-kro-mat-op'-se-ah).  (Gr.  a  = 
kicking,  chroma  =  color,  eye.)  Total  color- 
blindness. 

Achromatosis  (ah-kro-mat-o'-sis).  Any  disease 
marked  by  lack  of  pigmentation. 

Acorea  (ah-ko'-re-ah).  (Gr.  a  -  not  -}-  kore  -  pu- 
pil.)   When  the  pupil  is  absent. 


12  1J:\\  IS    I«  'CKKT 

Acquired.  Not  born  with,  but  dfV<*Ioped  aft«T 
birth. 

Acuity  (ak  u'-it-o).  ( L.  acuere  to  sharpt'ii.i 
Sharpn»'ss.  like  a  iieodlo.  The  sharpiK'Hs  of 
vision;  thi'  keenness  of  the  visual  powers.  The 
acuteness  of  vision  niran.s  the  vision  the  patient 
has  with  his  full  correction.  The  faculty  of  the 
retina  to  perceive  forms  depends  on  many  con 
ditions: 

1.  rriniarily,  on  the  sensibility  of  the  retina. 

2.  On  the  adaptation  of  the  retina. 

3.  On  the  general  illumination. 

4.  On  the  sharpness  of  the  retinal  inumf. 

5.  On  the  intensity  of  the  illumination. 

It  is  known  that  the  acuteness  of  vision  varies 
with  the  general  illumination  up  to  a  certain 
degree  of  intensity,  as  that  of  a  clear,  sunny 
day;  the  two  then  vary  in  a  direct  proportion, 
but  when  the  illumination  passes  a  certain  limit 
of  intensity,  the  acuteness  of  vision  diminishes 
instead  of  Increases. 

Adaptation  (ad  apta'shun ).  iL  adaptare  to 
adapt.)    Adjustment  of  th««  pupil  lo  light. 

Addition  ladish'-on).  ( L.  addrre  to  increase.  > 
The  uniting  of  two  or  more  nimibnrs  in  one 
sum. 

Adducens  ( ad  du'-sens ).  (L.  ad  -  towards,  du 
cere  to  lead.)  When  this  term  is  applied  to 
the  eye  it  means  the  ijiternal  rectus  muscle,  tho 
muscle  which  turns  the  eyeball  inward  toward 
the  nose,  supplied  by  the  third  cranial  or  motor 
ocull  nerve.  The  power  of  adduction  of  the  eye 
ranges  from  I'O  up  to  ."io  degrees.  For  testing 
the   power  of   th«'   adducens   or    internal    rectus 


OPHTHALMIC  DICTIONARY  13 

muscle,  use  the  strongest  prism,  base  out,  with 
which  the  eyes  can  overcome  diplopia. 

Adduct  (L.  adducere  =  to  bring  toward).  To  draw 
inward  toward  a  center. 

Adduction.  Movement  of  the  eyeball  inward  from 
its  position  of  rest.  The  adducens  means  the 
internal  rectus  muscle  by  which  we  turn  the 
eyes  inward.  The  test  for  the  power  of  the 
adducens  is  made  by  first  correcting  any  error 
of  refraction  and  have  the  patient  look  at  a 
light  20  feet  away,  placing  the  base  out  of  the 
strongest  prism,  with  which  the  eyes  can  over- 
come diplopia.  We  figure  from  their  position  of 
rest  and  this  prism  registers  the  adduction. 

Adenectomy  (ad-en-ek'-to"-me).  (Gr.  aden  =  giant! 
+  ektome  =  excision.)  Removal  of  a  gland  by 
operation. 

Adenemphraxis  (Gr.  aden  =  gland  +  emphraxis  = 
stoppage).  That  condition  in  which  the  duct  or 
gland  is  obstructed. 

Adenoid  (ad'-en-oid).  (Gr.  aden  =  gland  +  edois 
=  appearance.)    Resembling  a  gland. 

Adenclogaditis  (ad'-en-o-log-ad-i-tis').  Inflammation 
of  the  glands  of  the  eyes  and  conjunctiva.  Oph- 
thalmia neonatorum. 

Adenophthalmia  (ad-en-off-thal'-me-ah).  (Gr.  ad^n 
^^  gland  4-  ophthalmos  =  eye.)  Inflammation  of 
the  meibomian  glands. 

Aditus  (ad'-i-tis).  (L.  "a  passage.")  The  entrance 
to  a  canal  or  duct.  Aditus  Orbitae,  the  opening 
of  the  orbit,  covered  by  the  eyelids. 

Advancement.  The  cutting  away  of  a  muscle  of 
the  eye  and  attaching  it  to  an  advanced  point. 


This  operation  is  performed  on  the  weak  muscle 
in  cases  of  strabismus. 

Adventitious  (ad-ven-tish'-us).  Acquired — not  nor- 
mal. 

Afferent  (L.  ad  =  to  vf  ferre  =^  to  bear).  Convey- 
ing from  the  surface  to  the  center,  as  a  nerve 
or  vein. 

Albinism  (al'-bin-ism).  (L.  albus  ==  white.)  Ab- 
normal deficiency  of  pigment  in  the  iris  and 
choroid. 

Albugo    (al-bu'-go).    White  opacity  of  the  cornea 

of  the  eye.   Leukoma. 
Alexia  (a-lex'-ia).    (Gr.  a  =  lacking,  lexia  =  word.) 

Unable  to  read,  due  to  a  central  lesion. 

Amaurosis  Tam-aw-ro'-sis).  (Gr.  amaurotin  =  to 
render  obscure.)  A  disease  of  the  optic  nerve 
or  retina,  which  causes  blindness. 

Ambiopia  Cam-be-o'-pe-ah).  (Gr.  ambo  =  both, 
opia  ^  eye.)    Vision  with  both  eyes. 

Amblyopia  (am-ble-o'-pe-ah).  (Gr.  amblys  =  blunt 
+  opsis  =  sight.)  A  dimness  of  vision  from  de- 
fective sensibility  of  the  retina.  A  condition  in 
which  there  is  a  possibility  of  restoring  the 
former  vision;  for  instance,  when  a  person  has 
an  error  of  refraction  in  one  eye,  the  other  eye 
being  emmetropic,  he  will  learn  to  ignore  the 
eye  with  the  error,  and  use  the  one  with  the 
best  vision.  In  this  way  the  sight  will  become 
dim  from  want  of  use,  and  is  an  acquired  state, 
which  by  testing  with  ihe  pinhole  disc  will  show 
no  improvement.  Under  these  conditions,  the 
error  must  be  corrected  with  the  retinoscope. 
and  if  the  eyes  are  not  more  than  two  dioptrics 


OPHTHALMIC  DICTIONARY  15 

apart,  instruct  your  patient  always  to  wear  his 
correction  and  cover  the  good  eye  two  or  three 
times  a  day,  for  a  period  of  ten  minutes  at  a 
time,  and  try  to  use  the  amblyopic  eye.  In  this 
w^ay  you  will  notice  an  improvement  of  vision 
each  week.  When  the  pinhole  disc  fails  to  im- 
prove vision,  the  eye  is  either  amblyopic  or  in 
a  diseased  state.  Toxic  Amblyopia  is  a  dimness 
of  vision  from  the  poisonous  effect  of  drugs, 
such  as  quinine,  upon  the  nervous  system;  ex- 
cessive use  of  tobacco  or  alcoholic  stimulants 
produce  the  same  effect.  The  treatment  for  this 
form  of  Amblyopia  does  not  consist  of  glasses,- 
but  the  patient  must  quit  the  use  of  the  drug 
causing  the  trouble,  and  if  not  too  far  advanced 
there  is  a  possibility  of  recovering  the  former 
vision.  A.,  Postmar'ital,  that  due  to  sexual  ex- 
cess.   A.,  Crossed,  on  one-half  of  retina. 

Amblyopia  ex  Anopsia.  Amblyopia  resulting  from 
one  eye  having  been  excluded  for  some  time 
from  binocular  vision. 

Ametrometer  (a-met-rom'-e-ter).  (Gr.  a  =  lacking 
+  metron  =  measure.)  An  instrument  used  for 
measuring  ametropia. 

Ametropia  (a-met-ro'-pe-ah).  (Gr.  a  =  lacking, 
metron  :=  measure,  ops  =  eye.)  Any  error  of 
refraction,  such  as  hyperopia,  myopia,  or  astig- 
matism. Axial  Ametropia.  Ametropia  that  is 
caused  by  the  length  of  the  eyeball  on  the  optic 
axis.   The  opposite  of  Emmetropia. 

Amphice'lous  (Gr.  amphi  =  on  both  sides  -|-  koi- 
los  =  hollow).   Concave  on  both  sides  or  ends. 

Amphodiplopia    (am-fo-dip-lo'-pe-ah).     (Gr.   ampho 


=  both  +  diploos  =  double.)       That      condition 
where  both  eyes  have  double  vision. 

Amplifier  (am'-ple-fi-er).  An  apparatus  for  in- 
creasing the  magnifying  power  of  a  microscope. 

Amplitude  (am'-pli-tud).  State  of  being  ample. 
(Physics)  The  extent  of  a  movement  measured 
from  the  starting  point  or  position  of  rest. 
(Math.)  An  angle  upon  which  the  value  of  some 
function  depends. 

Amplitude  of  Convergence.    (See  Convergence.) 

Amyosta'sia  (Gr.  a  =  not  +  mys  =  muscle  +  sta- 
sis =  standing).   Nervous  tremor  of  the  muscles. 

Amyosthe'nia  (Gr.  a  =  not -f- mys  =  muscle -f  sthe- 
nos  =  strength).    Failure  of  muscular  strength. 

Anacamptom'eter.  An  instrument  for  measuring 
the  reflexes. 

Anaclasis  (an-ak'-las-is).  (Gr.  bending  back,  re- 
flection.) When  this  term  is  applied  to  light,  it 
refers  to  the  rays  traveling  obliquely  from  a 
rarer  to  a  denser  medium,  being  bent  backward 
toward  the  perpendicular  (refraction). 

Anaesthesia  (an-es-the'-ze-ah).  (Gr,  an  =  not -|- 
aisthesis  =  sensation. )  Lacking  sensitiveness, 
where  the  retina  is  amblyopic. 

Anaesthetic  (an-es-thet'-ik).  The  name  given  to 
that  which  produces  insensibility  to  pain,  as 
chloroform,  cocaine,  and  ether. 

Analysis  fa-nal'-i-sis).  (Gr.  "a  releasing.")  A  reso- 
lution of  a  whole  into  its  parts;  a  form  of 
reasoning  from  a  whole  to  its  parts. 

Anaphoria  (an-a-phor'-ia).  (Gr.  ana  =  up  +  phoria 
=  tending.)  That  condition  in  which  the  eyes 
turn  upward  when  the  e?^trinsic  muscles  are  in 


OPHTHALMIC  DICTIONARY  17 

a  state  of  rest.    Stevens   gives  33   degrees   for 
the  maximum  elevation. 

Anastomosis  (a-nas-to-mo'-sis).  (Gr.  anastomoo  = 
"througti  a  mouth.")  The  junction  of  vessels; 
the  joining  of  blood-vessels  with  one  another 
by  means  of  branches,  whereby,  if  the  fluid  be 
arrested  in  its  course  through  one  vessel,  it 
will  proceed  through  others.  The  term  is  some- 
times applied  to  the  junction  of  nerve  filaments 
with  each  other. 

Anerythrop'sia.    Red-blindness. 

Antecedent  (an-te-se'-dent).  (L.  antecedere  =  to 
go  before.)    The  first  of  two  terms  of  a  ratio. 

Anatomy  (a-nat'-o-me).  (Gr.  anatome  =  dissec- 
tion; ana  =:  up,  tome  =  a  cutting.)  (Eye.)  Re- 
lates to  the  description  of  the  structures  of  the 
eye  and  its  parts.  The  eyeball  is  nearly  sphe- 
rical in  shape  and  measures  about  24  mm.  in 
diameter.  The  cornea  represents  a  segment  of 
a  small  sphere  projecting  from  its  anterior  sur- 
face. The  first  tunic  of  the  eyeball  is  the  scle- 
rotic and  cornea.  The  posterior  five-sixths  is 
the  sclerotic,  which  is  white  and  opaque,  and 
serves  tcT  give  shape  to  the  eye  and  protects  its 
more  delicate  interior.  Near  the  posterior  pole, 
on  the  nasal  side,  is  a  sieve-like  disc  known  as 
the  lamina  cribrosa,  through  which  the  optic 
nerve  fibers  enter  the  eye.  The  sclerotic  is 
thickest  at  its  posterior  portion  and  gradually 
becomes  thinner  as  it  approaches  the  equator, 
and  again  thickens  as  it  approaches  the  cornea. 
The  anterior  one-sixth  is  the  cornea.  It  is  trans- 
parent and  of  a  greater  curvature  than  the  scle- 
rotic.   The  cornea  is  set  in  the  sclerotic  as  a 


18 


LEWIS  POCKET 


Nvatch  crystal  is  placed  in  its  frame,  and  is  com- 
posed of  five  layers,  from  without  inward  as 
follows:  Conjunctiva  Epithelium,  Bowman's 
Membrane.  Cornea  Proper,  Membrane  of  Desce- 
met.  and  the  Endothelium.  At  the  inner  angle 
(angle  of  filtration)  between  the  iris  and  cor- 
nea, there  are  a  number  of  comb-like  openings 
which  are  in  the  trabecular  tissue  or  pectinate 


ligament  which  runs  from  the  periphery  ot  thr 
cornea  to  the  base  of  the  iris.  These  openings 
are  called  the  spaces  of  Fontana.  through  which 
the  aqueous  humor  passes  into  the  canal  of 
Schlemm,  a  circular  canal  extending  around  the 
periphery  of  the  cornea   at   the  sclero  corneal 


on  I'm  A!. Mir  du^pionaijv 


1J> 


junction.  From  this  canal  the  humor  passes  into 
the  anterior  ciliary  veins.  The  socoiui  (uiiic  of 
the  oyo  is  comi)()so(l  o['  (he  choroid.  ciliar>'  btxly. 
and  the  iris.  It  lines  tlie  iiuuM-  side  of  the  scle 
rotic.  and  is  ixM'forated  to  aHow  llu'  optic  nerve 
to  entiT,   and   has  a  circular  opening   in    front, 


VENfl  VORTItOSn 


I'ul    .sluiwiufv    .Sci'Oiul    Tunic. 

which  is  known  as  (he  pupil.  Through  (his  (unie 
the  eye  obtains  i(s  principal  blood  and  nerve 
supply.  This  is  the  tunic  in  which  (he  pignuMU 
is  deposited  for  the  purpose  of  absorbing  ligh(. 
The  choroid  is  said  to  nourish  (he  reiina  and 
the  vitreous.  The  ciliary  muscles  are  within  (he 
ciliary  body,  and  are  used  for  acc()mnu)(la(ing. 
The  iris  is  the  most  anterior  por(ion  of  (he 
second  tunic.  It  is  located  in  front  of  the  crys- 
talline lens,  and  separales  the  an(erior  and  pos 
terior  chambers;  it  gives  tlie  t\ve  i(s  coloi-, 
regulates  the  amount  of  light  which  enters,  and 
prevents  sphori(!a.l  ab(Mration  of  the  lens.  The 
(liird  (unic  is  (lie  r(>(ina.  1(  is  a  very  delicate, 
transparent  membrane,  made  up  of  t(^n  layers, 
one  of  which  is  (he  layer  of  optic  nerve  libers. 
These  libers  pass  tlirough  (h<'  lamina  cribrosa 
at  the  op(ic  disc,  and  lla((en  ou(  more  and  more 


JV 


LEAVis  POCKET 


k 


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>t 


1 ,     A  n  fr  1  o 


OPHTHALMIC  DICTIONARY  21 

as  they  approach  the  front  of  the  eye.  The 
retina  is  attached  in  two  places,  at  the  optic 
disc  and  at  its  anterior  border,  the  ora  serrata. 
It  is  not  attached  to  the  choroid,  but  simply  lies 
on  it.  In  examining  the  retina  with  the  ophthal- 
moscope you  will  notice  the  optic  disc  on  the 
nasal  side,  which  marl^s  the  entrance  of  the 
optic  nerve  into  the  globe.  The  macula  lutea, 
w^hich  is  the  most  sensitive  spot  of  the  retina 
(sometimes  called  the  yellow  spot,  as  it  is  said 
to  turn  yellow  after  death),  is  situated  slightly 
on  the  temple  side.  The  function  of  the  retina 
is  to  receive  the  impressions  of  the  waves  of 
light  and  transmit  them  through  the  optic  nerve 
to  the  brain.  The  space  between  the  iris  and 
cornea  is  known  as  the  anterior  chamber  of  the 
eye,  and  that  between  the  iris  and  the  lens,  as 
the  posterior  chamber.  Both  of  these  chambers 
are  filled  with  a  transparent,  watery  fluid  known 
as  the  aqueous  humor.  The  large  chamber  back 
of  the  crystalline  lens  is  known  as  the  vitreous 
chamber,  and  contains  the  vitreous  humor, 
which  occupies  a  little  more  than  three-fourths 
of  the  eyeball.  It  is  a  perfectly  transparent  sub- 
stance, about  the  consistency  of  the  white  of  an 
egg,  and  is  enclosed  in  a  thin  transparent  sac 
known  as  the  hyaloid  membrane.  This  mem- 
brane divides  at  the  ciliary  body  and  forms 
what  is  known  as  the  anterior  and  posterior 
suspensory  ligaments,  which  are  attached  to  the 
lens  capsule,  thus  forming  what  is  known  as 
Petit's  Canal  and  the  Zonule  of  Zinn.  Within 
the  lens  capsule  the  crystalline '  lens  is  to 
be  found.  In  shape  the  lens  resembles  a  bi- 
convexed  lens,  except  that  it  is  less  curved  in 


22  LEWIS  POCKET 

front  than  behind;  in  youth  it  is  highly  elastic, 
moderately  firm,  yet  a  perfectly  transparent 
body,  as  clear  as  a  crystal,  and  as  we  grow 
older  it  becomes  harder  and  sometimes  of  a 
slightly  straw  tint.  The  crystalline  lens  is  made 
up  of  layers  closely  resembling  those  of  an 
onion,  which  accounts  for  its  elasticity.  The 
eyeball  is  imbedded  in  the  fatty  substance  of 
the  orbit,  and  is  surrounded  by  a  thin  mem- 
branous sac,  which  isolates  it  and  at  the  same 
time  allows  free  movement.  This  sac  is  named 
the  Capsule  of  Tenon.  It  is  a  very  delicate 
membrane,  consisting  of  two  layers  which  in- 
vest the  posterior  part  of  the  globe  from  the 
margin  of  the  cornea  backward  to  the  entrance 
of  the  optic  nerve,  and  is  connected  to  it  by  a 
very  delicate  connective  tissue.  Both  layers  are 
lined  on  the  inner  surface  by  endothelial  cells. 
The  cavity  between  them  is  continuous  with 
the  space  between  the  two  layers  of  the  sheath 
of  the  optic  nerve,  w^hich  is  known  as  the  sub- 
arachnoid space.  The  inner  layer  is  known  as 
the  pia  mater,  and  the  outer  as  the  dura  mater, 
and  between  them  empty  the  lymphatic  vessels 
of  the  sclerotic.  This  capsule  is  penetrated  by 
the  (tendon)  muscles  of  the  eyeball  near  their 
insertion,  which  spread  out  fan  shape  and  are 
attached  to  the  sclerotic. 

Anatomist  <a-nat'-o-mist),  A  person  who  is  skilled 
in  anatomy. 

Anatomy  of  Orbits.    See  Orbit. 

Anatro'pia  (Gr.  ana  =  up  +  trope  =  a  turning). 
That  condition  in  which  the  eyes  turn  up. 

Angle.  A  figure  formed  by  two  straight  lines  ex- 
tending out  from  one  point   in  different  direc- 


OPHTHALMIC  DICTIONARY  23 

tions.  Acute  Angle  is  an  angle  less  than  a  right 
angle,  or  less  than  90  degrees.  Adjacent  or 
Contiguous  angles  are  such  as  have  one  leg 
common  to  both  angles.  Angle  Alpha  is  the 
angle  formed  by  the  optic  and  visual  axis. 
Angular  Aperture  is  the  angle  formed  at  the 
focal  point  of  a  microscope  by  the  most  diver* 
gent  rays  which  enter  the  objective  lens.  Angle 
of  Convergence  is  the.  angle  which  the  two 
visual  axes  form  in  turning  from  their  position 
of  rest  to  a  point  less  remote.  The  angle  formed 
by  the  eyes  turning  from  parallelism  until  the 
visual  axes  are  directed  to  a  point  one  meter 
distant  on  the  median  line,  is  called  a  meter 
angle  of  convergence  and  is  the  unit  of  the 
angle  of  convergence.  When  the  visual  axes 
meet  on  the  median  line,  at  a  half  meter  dis- 
tance, it  is  called  a  two-meter  angle  of  con- 
vergence, and  when  looking  at  a  third  meter 
distance  it  is  called  a  three-meter  angle  of  con- 
vergence. Critical  Angle  is  the  angle  beyond 
which  a  ray  of  light  passing  from  a  higher  to 
a  less  refractive  medium  cannot  emerge.  Angle 
of  Deviation  is  the  angle  formed  between  the 
direction  of  the  incident  and  emergent  rays, 
and  shows  the  total  deflection.  Angle  of  Gamma 
is  the  angle  formed  at  the  center  of  rotation  of 
the  eye  by  the  optic  axis  and  a  line  drawn  from 
the  point  on  the  object  looked  at.  It  varies  with 
the  refraction  of  the  eye,  and  in  emmetropia  is 
about  5°;  it  increases  in  hyperopia  and 
decreases  in  myopia.  Angle  of  Incidence  is  the 
angle  formed  by  the  incident  ray  with  the  per- 
pendicular at  the  surface.  Angle  of  Iris  is  the 
angle  between  the  iris  and  the  cornea  at  the 


periphery  of  the  anterior  chamber  of  the  eye. 
Meter  Angle  (for  description,  see  under  Meter 
Angle).  Minute  Angle  is  an  angle  formed  by 
two  straight  lines  that  have  traveled  twenty 
feet  distant  from  a  point  and  separated  the 
sixtieth  part  of  a  degree.  Oblique  Angle  is  an 
angle  acute  or  obtuse,  in  opposition  to  a  right 
angle.  Obtuse  Angle  is  an  angle  greater  than  a 
right  angle  or  more  than  90  degrees.  Optic 
Angle  is  the  angle  included  between  the  optic 
axes  of  the  two  eyes  when  directed  to  the  same 
point.  Angle  of  Prism  is  the  angle  formed  by 
the  surfaces  of  the  prism  which  incline  to  each 
other.  Angle  of  Reflection  is  an  angle  formed 
by  the  reflected  ray  with  a  line  perpendicular 
to  the  reflecting  surface,  and  is  always  equal  to 
the  Angle  of  Incidence.  Angle  of  Refraction  is 
the  angle  formed  by  the  refracted  ray  with  the 
perpendicular.  Right  Angle  is  an  angle  formed 
by  a  right  line  falling  on  another  perpendicu- 
larly, or  an  angle  of  90  degrees.  Angle  of  Stra- 
bismus is  the  angle  formed  by  the  deviating  eye 
with  that  of  its  fellow.  Visual  Angle  is  the 
angle  formed  between  straight  lines  drawn  from 
the  boundaries  of  the  object  looked  at  and 
crossing  the  optical  center  of  the  eye. 

Anian'thlnopsy  (Gr.  an  —  not  -f  ianthinos  =  violet 
colored  +  opsis  =  vision).  Inability  to  distin- 
guish violet  shades. 

Aniridia  (an-ir-id'-e-ah).  (Gr.  an  =  not  +  iris.) 
Congenital  absence  of  the  iris. 

Anisocoria  fan-is-o-ko'-re-ah).  (Gr.  anisos  =  un- 
equal -f  koro  =^  pupil. )  That  condition  where 
the  two  pupils  are  unequal. 


OPHTHALMIC  DICTIONARY  25 

Anisometropia  (an-is-o-me-tro'-pe-ah).  (Gr.  an  = 
not,  iso  ^  equal,  metron  =  measure,  ops  =-  eye.) 
A  difference  of  refraction  in  the  two  eyes.  The 
defect  is  usually  congenital,  but  it  can  be  ac- 
quired, as  in  Aphakia,  or  operations  of  any 
kind.  One  eye  may  be  emmetropic,  the  other 
hypermetropic,  or  myopic,  or  one  more  hyper- 
metropic, myopic,  or  astigmatic  than  the  other. 
When  one  eye  is  hypermetropic  or  emmetropic, 
and  the  other  myopic,  the  hypermetropic  or 
emmetropic  eye  is  used  for  distance,  and  the 
myopic  eye  for  near-vision. 

Anisopia  (an-is-o'-pe-ah).  (Gr.  an  =  not,  iso  = 
equal,  ops  ^=  eye.)  An  inability  of  both  eyes  to 
receive  equal  impressions,  not  due  to  an  un- 
equal refractive  state. 

Anisosthenic  (an-i-sos-then'-ik).  (Gr.  anisos  =  un- 
equal +  sthenos  =  strength.)  Of  an  unequal 
strength,  as  when  the  muscles  of  the  eyes  are 
unequal  in  power. 

Anisotropous,  anisotropal,  anisotropic  (Gr.  anison 
^=  unequal  +  tropos  =^  a  turning).  Producing 
double  refraction  of  a  transmitted  ray  of  light. 

Ankyloblepharon  (ang-kil-o-blef'-ar-on).  Adhesions 
of  the  edges  of  the  eyelids. 

An'nular  Muscle.  A  ring-shaped  muscle  (as  the 
sphincter  muscle  of  the  iris). 

Annulus  (an'-nu-lus).  A  ring-shaped  organ.  A. 
ci Maris,  boundary  between  iris  and  choroid. 

Anomaly  (a-nom'-a-ly).  (Gr,  anomalia  =  irregu- 
larity.)   Deviation  from  normal  standard. 

Anoopsia  (an-o-op'-se-ah).  Where  the  eye  has 
turned  upward.    (Strabismus.) 


20  JLfcJWlS   FUCKKT 

Anophthalmia  (an-off-thal'-me-ah).  (Gr.  an  =  not 
+  ophthalmos  =  eye.)    Absence  of  the  eyes. 

Anopia  (ano'pia).  (Gr.  an  =  without  +  ops  = 
eye).   Congenital  absence  of  the  eye,  or  eyes. 

Anopsia  (an-op'-se-ah).  (Gr.  an  =  not  +  opsis  = 
sight.)  Disuse  of  the  eye  from  certain  defects, 
such  as  cataract,  amblyopia,  and  high  refractive 
errors. 

Anorthopia  (an-or-tho'-pe-ah).  (Gr.  an  =  not + 
orthos  =  straight  +  ops  =^  eye.)  A  defective 
state  of  vision  which  is  unable  to  distinguish  a 
want  of  parallelism. 

Anterior  (front  part).  Referring  to  the  eye,  the 
cornea  would  be  the  most  anterior  point. 

Antimetropia  (an-ti-me-tro'-pe-ah).  (Gr.  anti  = 
opposite,  metron  =  measure.)  Where  one  eye 
is  myopic  and  the  other  hypermetropic. 

Antiseptic  (an-ti-sep'-tik).  (Gr.  anti  =  against  + 
septic  =  putrid.)  A  substance  which  is  destruc- 
tive to  poisonous  germs. 

Aorta  (a-or'-ta).  (Gr.  aeiro  =  to  lift,  raise.)  The 
great  main  trunk  of  the  arterial  system,  pro- 
ceeding from  the  left  ventricle  of  the  heart, 
giving  origin  to  all  the  arteries  except  the  pul- 
monary (lungs). 

Apex  (a'-pex).  (L.,  summit  or  tip.)  The  thin  edge 
of  a  prism. 

Aphacia.    See  Aphakia, 

Aphakia  (ah-fa'-ke-ah).  (Gr.  a  =  lacking,  phakos 
=  lens.)    Absence  of  the  crystalline  lens. 

Aphose  (ah-foz').  (Gr.  a  =  without  +  phos  = 
light.)  Any  visual  sensation  due  to  absence  or 
interruption  of  light. 


OPHTHALMIC  DICTIONARY  27 

Apical  (a'-pik-al).   Pertaining  to  the  apex, 

Aplanatic  (ah-plan-at'-ik).  (Gr.  a  =  not  +  plane- 
tos  =  wandering.)  Tliat  condition  where  there 
is  neither  spherical  nor  chromatic  aberration, 
and  the  lines  are  also  straight.     (See  Lens.) 

Aponeurosis  (ap-on-u-ro'-sis).  (Gr.  apo  =  from + 
neuron  =  sinew.)  A  fibrous  band  investing  mus- 
cles and  connecting  them  with  tendons.  It  is 
white,  fibrous,  and  destitute  of  nerves,  and  has 
very  little  blood. 

Apparent  Position.  The  position  apparently  occu- 
pied by  an  object  seen  through  a  refracting 
medium,  as  distinguished  from  its  real  position. 

Appendages  of  the  Eye  are  the  orbits,  the  eye- 
brows, the  eyelids,  the  conjunctiva,  the  lach- 
rymal apparatus,  the  muscles,  the  aponeurosis, 
and  vessels  and  nerves  of  the  orbit. 

Applanatio-corneae  (ap-lan-a'-she-o-kor'-ne-e).  A 
condition  in  which  the  cornea  becomes  flat- 
tened. 

Applana'tion  (L.  ad  =  to  +  planare  =  to  flatten). 
Flattening  of  a  normally  convex  surface. 

Approximation  (a-prok-si-ma'-shon).  (L.  ad  =  to 
-f  proximare  =  to  come  near.)  A  continual  ap- 
proach to  a  true  result.  A  result  so  near  the 
truth  as  to  be  sufficient  for  a  given  purpose. 

Aqueous  Humor  (a'-que-us  hu'-mor).  (L.  aqua  = 
water,  humor  =  moist.)  A  transparent,  watery 
fluid  which  fills  the  anterior  and  posterior 
chambers  of  the  eye,  the  iris  becoming  the 
boundary  line  between  the  two  chambers. 
Weight,  5  grains.  Composed  of  water,  albumen, 
and  salts.    The  aqueous  is  a  secretion  formed  by 


2S  LEWIS   rOCKET 

the  epithelial  cells  lining  the  apices  of  the  cil- 
iary processes,  passing  through  the  pupii  and 
leaving  the  eye  through  Schlemms  Canal  to  pass 
into  the  anterior  ciliary  vein.  If  this  humor  is 
allowed  to  escape  it  will  re-form  again.  Its 
index  of  refraction  is  1.33. 

Aquocapsulitis  (,a'-kwo-caps-ii-li'-tis).  Serous  in- 
flammation of  the  iris. 

Arachnoid  (ar-ak*-noyd).  (Gr.  arachne  =  cobweb, 
eidos  =  resemblance.)  Resembling  a  spiders 
web. 

Arachnoid  Membrane  is  a  name  given  to 
several  membranes  which,  by  their  extreme 
fineness,  resemble  spider  webs.  The  delicate 
membrane  between  the  dura  mater  and  pia 
maier  of  the  optic  nerve  and  capsule  of  tenon. 

Subarachnoid  Space  is  located  between  the 
arachnoid  membrane  and  the  pia  mater.  It 
contains  the  greater  part  of  the  cerebrospinal 
fluid. 

Subdural  Space  is  located  between  the  dura 
mater  and  the  arachnoid  membrane,  and  con- 
tains a  small  amount  of  subdui'al  fluid. 

The  use  of  the  subarachnoid  or  cerebro-spinal 
fluid  is  to  mechanically  protect  the  nerve  cen- 
ters from  shock,  and  to  fill  tip  space,  as  fat  does 
in  other  parts  of  the  body.  Its  amount  is  esti- 
mated at  less  than  two  ounces. 

Arc  (ark).  (L.  arciis  =  bow.)  A  portion  of  a 
curved  line  or  segment  of  a  circle. 

Arcus  senilis  (ar'-kus  sen'-il-es).  (L.  arcus  —  bow. 
senilis  ^-  old.)  White  circle  in  cornea  near 
sclerotic.  The  arcus  is  first  noticed  as  two 
small  white  opaque  crescents,  one  above  and  the 


OPHTHALMIC  DICTIONARY  29 

other  below  within  the  margin  of  the  cornea, 
gradually  extending  until  the  ends  join,  form- 
ing a  ring.  The  arcus  will  increase  in  opacity 
more  than  in  width,  and  the  cornea  remains 
perfectly  transparent  within  its  circle  and  vision 
is  not  Impaired  by  it.  Cause,  fatty  degenera- 
tion.    Condition  in  aged. 

Area  of  Critical  Definition.  That  portion  of  an 
optical  image  within  which  the  detail  is  clearly 
defined. 

Argambiyopia      (ar-gam-ble-o'-pe-ah).      Amblyopia 

from  non-use  of  eye. 

Argyll-Robertson  Pupil.  A  pupil  that  will  not  re- 
spond to  light,  but  contracts  in  accomm.odation. 
Can  be  seen  in  locomotor-ataxia. 

Arithmetic  fa-rith'-me-tik).  (Gr.  arithmos  =  num- 
ber.)  The  theory  of  numbers,  the  art  of  com- 
putation, and  the  applications  of  numbers  to 
science  and  business. 

Artery  (ar'-tery).  (Gr.  tube.)  The  vessel  which 
carries  the  purified  blood  from  the  heart  to  the 
different  cells  of  the  body.  The  ophthalmic  ar- 
tery supplies  the  eye  with  blood  and  it  arises 
from  the  internal  carotid  artery  at  the  anterior 
clinoid  process  and  is  about  one-twelfth  of  an 
inch  in  diameter.  It  enters  the  orbit  through 
the  optic  foramen  below  and  on  the  temple  side 
of  the  optic  nerve.  It  then  passes  over  the 
nerve  to  the  inner  wall  of  the  orbit  and  runs 
forward  to  the  inner  angle  of  the  eye,  where  it 
divides  into  the  frontal  and  nasal  branches, 
which  may  be  divided  into  an  orbital  group.  It 
gives  off  the  lachrymal,  supra-orbital,  anterior 
and  posterior  ethmoidal,  palpebral,  frontal  and 


the   nasal,    muscular   anterior,    short   and    long 
ciliary,  and  the  central  artery  of  the  retina. 

The  short  ciliary  arteries  (six  to  ten  in  num- 
ber) enter  the  eye  through  the  sclerotic  around 
the  optic  nerve  to  supply  the  choroid  and  ciliary 
processes. 

The  long  ciliary  arteries  (two  in  number) 
pierce  the  sclerotic,  one  on  each  side  of  the  eye, 
and^run  forward  between  the  choroid  and  the 
sclerotic  to  the  ciliary  muscles,  which  they  sup- 
ply, and  they  join  the  anterior  ciliary  arteries. 

Th-e  anterior  ciliary  arteries  (five  to  eight  in 
number)  are  derived  from  the  muscular  and 
lachrymal  branches  of  the  ophthalmic.  They 
penetrate  the  sclerotic  about  a  sixteenth  of  an 
inch  from  the  corneal  margin,  and  finally  join 
the  long  posterior  ciliary  arteries  to  form  the 
circulus  arteriosus  iridis  major. 

The  arteria  centralis  retinae  is  the  first  and 
one  of  the  smallest  branches  of  the  ophthalmic 
artery.  It  pierces  the  optic  nerve  about  half  an 
inch  behind  the  eye  ball  and  runs  forward  to 
the  retina,  in  its  centre,  entering  the  eye 
through  an  opening  in  the  lamina  cribrosa. 
known  as  the  porus  opticus,  where  it  divides 
into  four  branches. 

Artificial  Eye.  A  thin  glass  plate  which  resembles 
the  sclerotic,  cornea  and  iris.  Artificial  eyes 
are  made  in  different  sizes  and  colors,  and  are 
always  fitted  to  match  the  sound  eye.  Before 
inserting  the  artificial  eye  it  should  be  put  into 
salt  and  water  for  a  few  minutes,  then  draw  the 
upper  lid  out  and  down,  and  slip  the  eye  up 
under;  then  draw  the  lower  lid  out  and  down, 
and  in  this  way  allow  the  eye  to  fall  into  posi- 


OPHTHALMIC  DICTIONARY 


31 


a-J.  LEWIS  I'OCKET 

tion.  As  a  rule,  an  artificial  eye  will  last  about 
a  year,  when  it  begins  to  lose  its  smoothness 
and  a  new  one  is  required. 

Artificial  Pupil.  One  made  by  an  operation 
(Iridectomy). 

Asep'sis.  Free  from  septic  matter,  or  free  from 
infection. 

Asthenopia  fas-then-o'-pi-ah).  (Gr.  a  =  lacking, 
sthenos  ==  strength,  ops  =  eye.)  Weak,  tired 
and  painful  vision;  the  result  of  straining  some 
part  of  the  mechanism  of  the  eye.  Vision  may 
be  normal.  It  is  subdivided  into  three  kinds: 
retinal,  muscular,  and  accommodative. 

Retinal.     Where  the  eye  cannot  stand  light 

without  pain;  intolerance  of  light;  photophobia. 

IVIuscular.     A  condition  of  the  eyes  in  which 

the  muscles  controlling  their  movement  suffer 

from  speedy  fatigue,  causing  pain. 

Accommodative.  Fatigue  of  the  ciliary  mus- 
cles by  hypermetropia,  presbyopia,  or  overwork 
in  emmetropia. 

Astigmagraph  (as-tig'-ma-graf).  An  instrument 
used  to  demonstrate  the  state  or  condition  of 
astigmatism  of  the  eye. 

Astigmatism  (as-tig'-mat-ism).  (Gr.  a  =  not + 
stigma  =  a  point.)  Astigmatism  is  a  term  ap- 
plied to  an  eye  whose  refraction  is  not  the 
same  in  all  its  parts,  causing  the  eye  to  focus 
the  light  at  different  points.  It  is  subdivided 
into  two  kinds,  regular  and  irregular.  Irregular 
astigmatism  is  where  there  is  a  difference  of 
refraction  in  one  and  the  same  meridian,  and 
according  to  some  authors,  is  subdivided  into 
normar  ana  abnormal.     Normal  irregular  astig- 


OPHTHALMIC  DICTIONARY  33 

matism  is  due  in  a  great  measure  to  irregulari- 
ties in  the  refracting  power  of  the  different 
sectors  of  the  lens,  and  causes  a  luminous  point 
to  appear  stellate,  or  star  shape.  The  abnormal 
variety  is  usually  caused  by  ulcers,  conical  cor- 
nea, or  injury  of  the  cornea,  but  the  same  con- 
dition may  be  congenital.  This  kind  of  astig- 
matism cannot  be  corrected  with  lenses.  Regu- 
lar astigmatism  is  where  we  have  the  meridians 
of  greatest  and  least  curvature  at  right  angles 
to  each  other,  and  are  known  as  the  principal 
meridians.  This  variety  can  be  corrected  with 
cylindrical  lenses.  It  has  five  subdivisions, 
which  merely  serve  to  show  the  location  of  the 
foci,  which  are  as  follows: 

No.  1.  Compound  Hyperopia  Astigmatism  is 
that  condition  in  which  the  foci  of  the  two  prin- 
cipal meridians  are  back  of  the  retina  at  differ- 
ent places  when  the  eye  is  at  rest  and  looking 
at  infinity. 


No.    1.      Compound   Hyperopic   Astigmatism. 

No.  2.  Simple  Hyperopic  Astigmatism  is  that 
condition  in  which  parallel  rays  enter  the  eye. 
and  one  of  the  principal  meridians  focuses  on 
the  retina,  the  other  behind  the  retina,  when 
the  eye  is  at  rest. 


34 


LEWIS  POCKET 


No.    2     Simple   Hyperopic   Astign^iatism. 

No.  3.  Compound  Myopic  Astigmatism  is 
that  condition  in  which  the  two  principal 
meridians  focus  in  front  of  the  retina  at  differ- 
ent places  when  the  eye  is  at  rest  and  looking 
at  infinity. 


No.  3.      Compound  Myopic  Astig-malism. 

No.  4.  Simple  Myopic  Astigmatism  is  that 
condition  in  which  one  of  the  principal  merid- 
ians focuses  on  the  retina  and  the  other  in 
front  with  the  eye  at  rest  and  looking  at 
infinity. 


No.    4.      Simple    Myopic    Astigmatism. 


OPHTHALMIC  DICTIONARY  35 

No.  5.  Mixed  Astigmatism  is  that  condition 
in  wliich  one  of  the  principal  meridians  focuses 
in  front  of  the  retina  and  the  other  behind  the 
retina  when  tlie  eye  is  at  rest  and  loolving  at 
infinity.  It  derives  its  name,  mixed  astigmatism, 
from  tlie  fact  that  one  meridian  is  hyperopic 
and  the  other  myopic. 


No.  5.      Mixed  Astigmatism. 

Corneal  Astigmatism  is  caused  by  irregularity 
of  the  curvature  of  the  cornea. 

Lenticular  Astigmatism  is  caused  by  an  irregu- 
larity of  the  curvature  of  the  crystalline  lens. 

Astigmatism  with  the  Rule  is  where  the  axis 
of  a  minus  cylinder  that  will  correct  the  astig- 
matism is  nearer  the  180th  meridian  than  the 
90th,  or  the  axis  of  a  plus  cylinder  that  will  cor- 
rect the  astigmatism  is  nearer  90  than  180; 
otherwise,  it  is  against  the  rule. 

Correcting  cases  of  high  astigmatism  often 
proves  unsatisfactory  at  the  time.  When  the 
image  is  formed  on  the  retina  of  such  an  eye  it 
is  much  blurred  at  one  of  the  principal  merid- 
ians, and  sometimes  distorted.  However,  the 
patient  accepts  this,  as  his  vision  has  never 
been  better.  So  much  so  that  when  the  correct 
lenses  form  a  distinct  retinal  image,  he  fails  to 
recognize  it,   and  will  sometimes  say  that  the 


36  LEWIS  POCKET 

object  looks  distorted,  as  the  fibers  of  his  optic 
nerve  are  somewhat  amblyopic,  and  therefore 
different  from  those  of  other  people.  In  such 
cases  the  brain  is  in  the  habit  of  accepting 
vision  from  parts  of  the  retina  that  are  most 
distinct,  and  when  wearing  their  correction  for 
the  first  time,  the  vision  shows  very  little  im- 
provement, if  any.  It  is  not  uncommon  for 
cases  of  say  4-D.,  of  astigmatism  to  see  very 
little  better  with  their  glasses  at  the  time  of 
fitting,  but  if  they  are  worn  persistently  the 
vision  is  expected  to  improve  in  a  few  months. 

Astigmom'eter.  An  instrument  for  measuring 
astigmatism, 

Astig'mometry.  The  study  of  measurement  of 
astigmatism. 

Astringent  (as-trin'-jent).  (L.  astringere  =  to 
contract.)  An  agent  that  causes  contraction 
and  arrests  discharges. 

Asymmetry  (ah-sim'-et-re).  (Gr.  a  =  not  +  syn  = 
with  +  metron  =  measure.)  When  the  eyes  do 
not  correspond,  or  resemble  each  other  in 
appearance,  they  are  said  to  lack  symmetry. 

Atax'ia.  (Gr.  a  =  not  +  taxis  =  order.)  Failure  of 
muscles  to  coordinate. 

Atom  (at'-om).  (Physics.)  An  ultimate  indi- 
visible particle  of  matter. 

Atonic  (aton'-ic).  (Gr.  atonia  =  languor.)  Relaxed; 
without  normal  tone  or  tension. 

Atrophy.  (Gr.  a  =  not  -f  trope  =  nourishment.)  A 
wasting  away  of  a  part  from  a  lack  of  nutrition. 

Atropine  (at'-ro-pin).  A  poisonous  alkaloid  ex- 
tracted from  atropa-belladonna,  or  deadly  night- 


OPHTHALMIC  DICTIONARY  61 

shade;  it  temporarily  paralyzes  the  sphincter 
iridis  (circular  muscles  of  the  iris)  and  the 
ciliary  muscles  within  the  eye,  consequently  the 
pupil  is  dilated  and  accommodation  fully  re- 
laxed, leaving  the  eye  adjusted  for  its  far  point 
of  vision  in  a  state  of  rest.  For  this  reason  it 
is  known  as  a  mydriatic  and  a  cycloplegic,  and 
is  used  more  than  any  other  to  suspend  accom- 
modation and  dilate  the  pupil.  Atropine  para- 
lyzes the  sphincter  muscle  of  the  iris  and  the 
ciliary  muscle,  and  hence  results  in  dilatation  of 
the  pupil,  and  also  an  inability  to  see  clearly 
near  by.  The  dilatation  of  the  pupil  is  a  maxi- 
mum one.  If,  in  the  case  of  a  dilatation  of  the 
pupil  caused  by  oculomotor  paralysis,  atropine 
is  instilled,  the  pupil  becomes  still  more  dilated. 
This  proves  that  atropine,  besides  producing 
paralysis  of  the  contracting  fibers,  causes  also 
stimulation  of  the  dilating  fibers.    The  effect  of 

.  the  atropine  makes  its  appearance  in  from  ten 
to  fifteen  minutes  after  the  instillation,  and 
soon  reaches  its  maximum.  Commencing  with 
the  third  day  it  begins  to  decrease  again,  but 
does  not  disappear  completely  until  after  the 
lapse  of  a  week.  The  instillation  of  atropine, 
therefore,  causes  the  patient  a  disturbance  of 
rather  long  duration,  and  hence  should  be  em- 
ployed only  when  there  is  good  reason  for  it. 

Atropinism  (at'-ro-pin-ism).  A  condition  produced 
by  the  use  of  atropine. 

At'ropinize.  To  put  under  the  influence  of 
atropine. 

Atypic  Hypermetropia  (at-ipMk).  Irregular  Hyper- 
metropia  caused  by  tumors  behind  the  eye,  ex- 
erting  such   a   pressure   on   the   posterior   pole 


38  LEWIS  POCKET 

that  the  region  of  the  macula  is  pushed  in  front 
of  the  principal  focus,  the  eye  thus  becoming 
hyperopic.  It  may  be  caused  by  detachment  of 
the  retina  in  the  region  of  the  macula. 

Atypic  Myopia  (at-ip'-ik).  Progressive  Myopia, 
caused  by  the  elongation  of  the  eye. 

Autophthalmoscope  (au-tof-thal'-mo-skope).  An 
ophthalmoscope  planned  in  such  a  way  that  a 
person  can  examine  his  own  eyes. 

Average  (av'-e-raj).  Etymology  obscure.  The  re- 
sult of  adding  several  quantities  and  dividing 
the  sum  by  the  number  of  quantities. 

Avoirdupois  (av'-or-du-poiz').  (Fr.  aver  =  goods  -f 
de  =  of  =  pois  =  weight.)  A  system  of  weight 
in  which  1  lb.  =  16  oz.  =  approximately  7,000 
troy  grains. 

Axial.    Of,  or  pertaining  to,  an  axis. 

Axial  Ametropia.  Ametropia  that  is  caused  by 
the  length  of  the  eyeball  on  the  optic  axis. 

Axially.    In  the  direction  of  the  axis. 

Axiom  (ak'-si-om).  (Gr.  axioma  ^  a  requisite,  a 
self-evident  principle.)  A  simple  statement,  of 
a  general  nature,  so  obvious  that  its  truth  may 
be  taken  for  granted. 

Axis  (aks'-i&).  A  straight  line,  real  or  imaginary, 
passing  through  the  center  of  a  body,  on  which 
it  may  revolve. 

Optic  A.  An  imaginary  line  through  all  cen- 
ters of  the  eye  from  before  back;  that  is,  the 
center  of  the  cornea,  through  the  nodal  points 
to  the  inner  side  of  the  macula  lutea. 

Visual  A.  A  line  from  the  macula  lutea 
through  the  optical  center  of  the  eye  to  the 
point  on  the  object  looked  at. 


OPHTHALMIC  DICTIONARY  39 

Major  A.  The  longest  diameter  of  the  cornea 
or  lens.     Minor  A  the  shortest. 

Principal  A.  A  line  which  passes  through  the 
optical  center  of  a  lens  at  right  angles  to  both 
sides,  it  is  the  only  ray  of  light  to  pass  through 
unrefracted. 

Secondary  A.  Any  line  crossing  the  principal 
axis  at  the  optical  center.  These  rays  are  re- 
fracted, but  emerge  in  the  same  direction  as 
they  entered. 

Axis  of  a  Cylinder.  The  only  meridian  of  a 
cylindrical  lens  without  focusing  power. 

Axis  of  Mirror.  A  line  which  strikes  the  cen- 
ter of  curvature  at  right  angles  to  the  surface 
is  called  its  axis. 

Axis  of  Refraction.  The  normal  to  the  surface 
of  a  refracting  medium  at  the  point  of  incidence 
of  a  ray  of  light. 
Axometer  (ax-om'-e-ter).  An  instrument  for  the 
determination  of  the  axis  and  focus  of  spherical, 
cylindrical  or  sphero-cylindrical  lenses. 


B 


ACILLAR    LAYER    (bas'-il-ar).    The   layer    of 
rods  and  cones  of  the  retina. 

Barom'-eter.  (Gr.  baros  =  weight  +  metron  = 
measure.)  An  instrument  indicating  the  atmos- 
pheric pressure. 

Basalis  Lamina,  or  membrane  of  Bruch.  The 
membrane  which  separates  the  ghoroid  from  the 
pigmentary  layer  of  the  retina. 

Base.  (L.  bassus  =  low.)  (a)  The  line  or  surface 
forming  that  part  of  a  figure  on  which  it  is  sup- 


40  LEWIS  POCKET 

posed  to  stand,  (b)  The  base  of  a  system  of 
logarithms  is  the  number  which,  raised  to  the 
power  indicated  by  the  logarithm,  gives  the 
number  to  which  the  logarithm  belongs,  (c)  In 
percentage,  the  number  which  is  multiplied  by 
the  rate  to  produce  the  percentage.  The  base 
of  a  prism  is  its  thickest  part. 

Base  Apex  Line.  A  straight  line  drawn  from  the 
thickest  to  the  thinnest  part  of  a  prism. 

Base  Curve.  The  meridian  of  least  refraction,  on 
the  toric  side  of  a  lens. 

Basedow's  Disease.     (See  exophthalmic  goiter.) 

Beer's  Knife.  A  knife  with  a  triangular  blade  for 
corneal  incision. 

Bi.  (L.  bis  =  twice.)  Is  employed  to  signify  two 
things  in  one;  for  instance,  bifocal,  biconcave, 
biconvex. 

Biconcave.    Concave  on  both  sides. 

Biconvex.     Convex  on  both  sides. 


Bifocal  (bi-fo'-.'^al).  Having  a  double  focus.  A 
lens  with  two  focal  lengths,  having  two  parts, 
the  upper  for  distance  and  the  lower  for  near 
vision.  They  can  be  made  up  in  five  different 
ways,  namely: 


No. 

1. 

One-piece  Bifocal. 

No. 

2. 

Split  or  Franklin  Bifocal 

No. 

3. 

Perfection  Bifocal. 

No. 

4. 

Cemented  Bifocal. 

No. 

5. 

Invisible  Bifocal. 

OPHTHALMIC  DICTIONARY  41 

The  one-piece  bifocal  is  made  of  glass  with 
the  same  density  throughout.  Its  double  focus 
is  governed  by  change  of  curvature.  It  can  be 
mounted  with  or  without  rims.  The  split  or 
Franklin  and  perfection  bifocals  must  be  worn 
in  rims,  while  the  cemented  and  also  invisible 
bifocals  can  be  worn  without  rims.  The  in- 
visible bifocal  lenses  are  made  by  fusing  under 
intense  heat,  two  pieces  of  curved  glass  with 
different  densities.  A  bifocal  lens  consists  of 
two  parts  of  two  different  foci.  In  hypermet- 
ropia  with  presbyopia,  or  old  sight,  the  upper  is 
the  weaker  for  distance,  the  lower  being 
stronger  for  near  objects.  In  myopia,  the  upper 
should  be  the  stronger  and  the  lower  the  weaker 
glass.  In  this  way  the  patient  has  good  distant 
vision  without  the  extra  strain  on  the  accom- 
modation. 

Canada  Balsam  is  used  in  cementing  bifocal 
lenses  in  the  following  manner:  First  be  sure 
that  the  lenses  are  perfectly  clean.  Then 
squeeze  a  small  drop  of  the  balsam  on  to  the 
large  lens,  and  press  the  scale  upon  the  balsam 
until  it  spreads  out  thoroughly  between  the 
glasses,  being  careful  not  to  break  the  lenses. 
Then  place  the  lenses  on  a  piece  of  metal  over 
a  small  flame,  and  heat  them  slowly  until  all 
the  bubbles  disappear,  and  until  the  balsam  is 
nearly  hard — just  about  hard  enough  to  take  a 
slight  impression  of  the  finger  nail.  It  is  impos- 
sible for  a  novice  to  accurately  judge  just  how 
much  to  heat  the  lenses,  but  with  practice  it 
becomes  a  simple  matter.  The  success  depends 
largely  on  their  being  heated  just  long  enough. 
If  they  are  not  heated  enough  they  will  slide 


42  LEWIS  POCKET 

out  of  position,  and  if  they  are  heated  too  much 
they  will  chip  off  very  easily. 

Binocular.  (L.  bis  =  twice,  oculus  ^  eye.)  Per- 
taining to  both" eyes.  In  vision  it  refers  to  the 
ability  of  both  eyes  to  see  the  same  point  of  an 
object  at  the  same  time.  To  prove  it  exists  a 
5°  prism  placed  base  up  or  down  over  one  eye 
should  make  the  object  looked  at  appear  double. 

Biorbital  Angle.    The  same  as  the  optic  angle. 

Birefractive.     Doubly  refractive. 

Bl-Spherical.    A  lens  with  a  sphere  on  both  sides. 

Blear-eye.    Marginal  blepharitis. 

Blennorrhea  (blen-or-e'-ah).  (Gr.  blennos  =  mu- 
cus +  rhoia  =  a  flow.)  Excessive  mucous  dis- 
charge. 

Blepharadenitis  (blef-ar-ad-en-i'-tis).  (Gr.  bleph- 
aron  =  eyelid  +  aden  =  gland  +  itis.)  Inflam- 
mation of  the  meibomian  glands. 

Blepharal  (blef'-ar-al).  (Gr.  blepharon  =  eyelid.) 
Pertaining  to  the  eyelids. 

Blepharelosis  (blef-ar-el-o'-sis).  Ingrowing  eye- 
lashes.    (See  Trichiasis.) 

Blepharism  (blef-ar-ism).  Where  there  is  an  in- 
ability on  the  part  of  4;he  patient  to  refrain  from 
winking.     (Blinking.) 

Blepharitis  (blef-ar-i'-tis).  (Gr.  blephron  =  eye- 
lid +  itis  =  inflammation.)  Inflammation  of  the 
eyelids.  Ciliaris  or  marginalis  b.  That  condi- 
tion where  the  hair  follicles  of  the  eyelid  are 
inflamed.  Squamosa  b.  A  marginal  blepharitis 
in  which  the  edges  of  the  lids  become  scaly. 
Uncerosa  b.  An  ulcerous  form  of  marginal 
blepharitis. 


OPHTHALMIC  DICTIONARY  43 

Blepharochalasis  (blef'-ar-o-kal'-as-is).  (Gr.  bleph- 
aron  =  eyelid  +  chalasis  =  a  slackening.)  Re- 
laxation of  the  skin  of  the  eyelid,  due  to  atrophy 
of  the  intercellular  tissue.  A  condition  in  which 
folds  of  the  skin  hang  down. 

Blepharoclonus  (blef-ar-ok-lo-nus).  (Gr.  bleph- 
aron  —  eyelid  +  klonos  =  a  tumult.)  Clonic 
spasm  of  the  eyelids. 

Blepharoconjunctivitis.  Inflammation  of  the  eye- 
lids and  conjunctiva. 

Blepharoncus  (blef-ar-ong'-kus).  (Gr.  blepharon  = 
eyelid  +  onkos  =  a  tumor.)  A  tumor  or  swell- 
ing of  the  eyelid. 

Blepharoplegia  (blef-ar-o-ple'-ge-ia).  (Gr.  bleph- 
aron ^  eyelid  +  plege  =  stroke.)  That  state  in 
which  the  eyelid  is  paralyzed,  causing  ptosis. 

Blepharoptosis  (blef-ar-op-to'-sis).  (Gr.  blepharon  = 
eyelid  +  ptosis  =  a  falling.)  That  condition 
where  the  upper  eyelid  droops  from  paralysis. 

Blepharopyorrhea.  (Gr.  blepharon  =^  eyelid  + 
pyon  =  pus  +  rhoia  =  I  flow.)  A  discharge  of 
mucus  from  the  eyelids. 

Blepharorrhaphy  (  blef-ar-or'-af-e).  (Gr,  bleph- 
aron =  eyelid  +  rhaphe  =  seam.)  The  stitch- 
ing together  of  a  part  of  the  edges  of  a  slit 
between  the  eyelids. 

Blepharospasm  (blef'-ar-o-spasm).  A  spasmodic 
contraction  of  the  orbicularis  palpebrarum  mus- 
cle, so  that  the  lids  are  firmly  pressed  against 
the  globe.  Occurs  where  photophobia  is  marked. 
It  is  reflex  from  the  irritation  of  the  fifth  nerve, 
and  occurs  in  neuralgia  of  its  branches;  in 
inflammation  of  the  conjunctiva  or  cornea;  from 
foreign  bodies;   errors  of  refraction,  etc. 


44  LEWIS  POCKET 

Blepharostat  (blef-ar'-o-stat).  (Gr.  blepharon  = 
eyelid  -f-  states  =  fixed.)  An  instrument  used 
for  holding  the  eyelids  apart. 

Blepharostenosis  (blef  ar-o-ste-no'-sis).  Gr. 
blepharon  =  eyelid  +  stenosis  =  a  narrowing.) 
A  narrowing  of  the  palpebral  slit  between  the 
eyelids. 

Blepharosynechia  (blef-ar-o-sin-ek'-i-a).  (Gr.  bleph- 
aron =  eyelid  +  synechia  =  continuity.)  A  con- 
dition in  which  there  is  a  growing  together  of 
the  eyelids. 

Blepharotomy  (blef-ar-ot'-o-me).  (Gr.  blepharon  = 
eyelid  +  tome  =^  incision.)  A  surgical  opera- 
tion for  the  cutting  of  the  eyelid. 

Blind.  Loss  of  sight.  Day-blindness  is  where 
vision  is  better  at  night.  Night-blindness  is  de- 
fective vision  at  night-time. 

Blind  Spot.  Also  known  as  the  optic  disc,  or 
optic  papilla.  It  marks  the  entrance  of  the 
optic  nerve  on  the  retina.    Not  sensitive  to  light. 

Blinking.  That  condition  in  which  there  is  an 
involuntary  winking. 

Blood  (blud).  A  red.  slightly  translucent  fluid 
which  circulates  in  the  p^i'incipal  vascular  sys- 
tem of  animals,  carrying  nourishment  to  all 
parts  of  the  body,  and  bringing  away  wa.ste 
products  to  be  excreted.  In  the  veins  its  color 
is  somewhat  darker,  owing  to  the  loss  of  oxygen 
while  passing  through  the  tissues. 

Blood  Vessels.     (See  veins  and  arteries.) 

Bonnet's  Capsule.    The  same  as  Tenon's  Capsule. 

Bowman's  Membrane.  The  second  anterior  layer 
of  the  cornea. 


1 


OlMITllALMIC  DICTIONARY  45 

Brachymetropia  (brach-e-me-tro'-pe-a).  (Gr.  bracli- 
us  =^  short,  metron  ^^^  measure,  ops  -=  eye.)  The 
same  as  myopia  and  hypometropia.  It  is  an 
eye  where  parallel  rays  of  light  will  focus  in 
front  of  the  retina  with  the  muscles  of  accom- 
modation at  rest. 

Brain.  The  organ  of  intellect.  A  nervous  mass 
within  the  skull  divided  into  many  parts. 

Brow-Ague.  Supra-orbital  neuralgia;  a  superficial 
pain  in  the  region  of  distribution  of  the  first 
division  of  the  fifth  nerve. 

Bruch's  Glands.  The  lymph-follicles  of  the  con- 
juctiva  of  tlie  lower  eyelid. 

Bruch's  Membrane.  The  inner  layer  of  the  choroid 
coat  of  the  eye. 

Bruch's  Muscle.     (See  Cilfary  Muscle.) 

Buphthalmia  (buf-thal'-me-ah).  (Gr.  bous  =  ox -f- 
ophthalmos  ^-  eye.)     Enlargement  of  the  eye. 

Buphthalmus.     (See  Buphthalmia.) 


^AMPIMETER  (kam-pim'-e-ter).  (L.  campus  = 
field  +  Gr.  metron  — ^  measure.)  An  instrument 
for  measuring  the  field  of  vision,  replaced  by 
perimeter. 

Canada  Balsam.  A  liquid  resin  obtained  from  the 
balsam-fir  tree,  which  grows  in  Canada.  It  is 
used  for  the  purpose  of  cementing  lenses  to- 
gether. It  is  easily  melted  if  heated,  and  readily 
soluble  in  alcohol.  (See  bifocal  for  its  use.) 
Index  of  refraction  1.52. 

Canallc'ulus.    A  small  canal  or  channel. 


46  LEWIS  rOCKET 

Canal  of  Cloquet.  The  name  given  to  Stilling's 
Canal  after  Jules  Germain  Cloquet,  Parisian 
surgeon,  1790-1883. 

Canal  of  Petit.  The  space  which  surrounds  the 
crystalline  lens  between  the  suspensory  liga- 
ments. 

Canal  of  Schlemm.  Circular  canal  surrounding 
the  eye  at  sclerocorneal  junction.  (See 
Anatomy.) 

Canal  of  Stilling.  The  canal  which  runs  through 
the  vitreous  humor  from  the  entrance  of  the 
optic  nerve  to  the  posterior  surface  of  the  lens. 
It  is  lined  by  the  hyaloid  membrane.  This 
canal  is  said  to  convey  the  minute  artery  from 
the  central  artery  of  the  retina  to  the  back  of 
the  lens,  during  development  of  the  eye.  The 
artery  then  disappears,  but  the  canal  remains. 
It  is  also  known  as  the  Hyaloid  Canal. 

Canals  of  Fontana.  A  number  of  little  spaces  or 
openings  between  the  iris  and  cornea,  in  the 
sclerotic.  (See  Spaces  of  Fontana;  also  see 
Schlemm's  Canal.) 

Cancel  (kan'-sel).  (L.  cancelli  =  a  lattice.)  Orig- 
inally to  draw  lines  across  a  calculation.  To 
strike  out  or  eliminate  as  a  common  factor  in 
the  terms  of  a  fraction,  a  common  term  in  the 
two  members  of  an  equation,  etc. 

Canthectomy  (kan-thek'-to-my).  (Gr.  kanthos. 
canthus  +  ektome  =  excision.)  An  operation  in 
which  part  of  the  canthus  is  cut  away. 

Ca nth  itis  (kan-thi'-tis) .  Inflammation  of  the  angles 
of  the  eyelids. 

Cantholysis.      (Gr.     kanthos,      canthus  +  lysis  = 


OPHTHALMIC  DICTIONARY  4T 

loosening.)    Incision  of  the  canthus  to  widen  the 
slit  between  the  lids. 

Canthoplasty  (kan'-tho-plas-te).  A  surgical  opera- 
tion for  lessening  the  pressure  and  friction  of 
the  upper  lid  by  cutting  the  outer  canthus. 
Plastic  c.  operation,  an  operation  for  restoring  a 
lost  part. 

Canthotomy  (kan-thot-'o-me).  An  operation  for 
the  slitting  of  either  canthus. 

Can'thus.  (Gr.  "angle  of  the  eye.")  The  angle 
at  the  junction  of  the  eyelids,  known  as  the. 
inner  and  outer  canthi. 

Cap'illary  (hair  like).  Any  one  of  the  little  ves- 
sels which  conduct  the  blood  from  the  arteries 
to  the  veins. 

Capsule  (kap'-sule).  (J^.  capsula  =  a  box.)  A  sac 
which  encloses  an  organ  for  the  purpose  of 
support,  protection  and  lubrication.  The  cap- 
sule of  the  eye  lens. 
Capsule  of  Tenon.  (See  Tenon's  Capsule.) 
Capsulitis  (kap-su-li'-tis).  Inflammation  of  the 
capsule  of  the  crystalline  lens. 

Capsulotomy  (kap-su-lot'-o-my).  An  operation  for 
the  cutting  of  a  capsule,  as  that  of  the  lens. 

Cardinal  Points  (that  on  which  a  thing  turns  or 
depends).  Points  which  play  an  important  part 
in  the  course  of  light  through  a  spherical  sur- 
face. There  are  four  in  number.  The  two  prin- 
cipal foci  and  the  two  nodal  points.  The  first 
principal  focus  is  the  point  from  which  light 
rays  emanate  and  pass  through  a  spherical  lens 
and  emerge  parallel  to  its  principal  axis.  The 
second  principal  focus  is  the  point  where  the 


4S  LEWIS  rOCKET 

emergent  rays  cross  each  other  when  the  inci- 
dent rays  have  been  parallel  to  the  principal 
axis.     (See  Nodal  Point.) 

Carotid  (ka-rot'-id).  (Gr.  karos  =  deep  sleep, 
stupor;  so  named  from  the  effect  of  pressing 
on  them.)  The  carotid  arteries  or  carotids  are 
the  two  great  arteries  of  the  neck,  that  convey 
the  blood  from  the  aorta  to  the  head,  brain  and 
eye.  The  common  carotids,  one  on  either  side 
of  the  neck,  divide  into  an  external  and  an 
internal  branch,  the  former  supplying  the  ex- 
terior of  the  skull. 

Cartilage  (kar'-til-aj).  (L.  Cartilago  =  gristle.) 
The  gristle  or  white  elastic  snbstEUice  in  differ- 
ent parts  of  the  body.     (See  Tarsus.) 

Cartilaginous  (kar-til-aj'-in-us).  Relating  to  or 
consisting  of  cartilage. 

Caruncula  Lachrymalis  (kar-un'-ku-.'ah).  (L.  a 
small  fleshy  mass.  L,  lacrima  =  a  tear.)  Is  the 
small  reddish  body  at  the  inner  canthus  of  the 
eye. 

Cast.  A  cast  in  the  eye  would  apply  to  strabismus. 

Cataplioria  (kat-a-fo'-re-ah).  (Gr.  kata  =  down, 
phoria  ==  "tending.")  That  condition  in  which 
one  of  the  eyes,  though  parallel  with  its  fellow 
when  in  use,  turns  downward  when  the  extrin- 
sic muscles  are  in  a  state  of  rest.  Esocataphoria 
is  the  tendency  of  the  visual  line  inward  and 
downward.  Exocataphoria  is  a  tendency  of  the 
visual  line  outward  and  downward. 

Cataract  (kat'-ar-akt).  (Gr.  kataraktes  —  to  break 
down.)  Any  opacity  of  the  crystalline  lens  or 
lens  capsule  of  the  eye.  Lenticular  c,  an 
opacity    of    the    lens    proper.      Capsular    c.    an 


OPHTHALMIC  DICTIONARY  49 

opacity  of  the  lens  capsule.  Senile  c,  an  opacity 
of  the  lens  due  to  age..  Traumatic  c,  a  catar- 
act due  to  an  injury.  Pyramidal  c,  an  opacity 
in  the  center,  yet  at  the  anterior  pole,  of  the 
lens.  Secondary  c,  a  cataract  appearing  after 
the  extraction  of  the  lens,  caused  by  that  part 
of  the  lens  capsule  still  attached  to  the  hyaloid 
membrane  becoming  opaque.  Cortical  c,  that 
condition  in  which  the  border  or  outer  layers  of 
the  lens  are  losing  their  transparency.  Hard  c. 
(See  Senile  c).  Soft  c,  where  the  lens  is  soft 
and  milky.  Polar  c,  an  opacity  confined  to  the 
anterior  or  posterior  pole  of  the  lens. 

Catacaustic.     (See  Caustic  surface.)^ 

Cat'adioptrical.  (Physics.)  Pertaining  to,  pro- 
duced by,  or  involving,  both  the  reflection  and 
refraction  of  light. 

Catopter  (kat-op'-ter).  (Gr.  kata  =  down  +  opto- 
mai  =  I  see.)  A  reflecting  optical  glass  or  in- 
strument; a  mirror. 

Catoptric  (kat-op'-trik).  Relating  to  that  branch 
of  optics  called  catoptrics;  pertaining  to  inci- 
dent and  reflected  light.  The  whole  doctrine  of 
catoptrics  is  founded  on  this  simple  principle 
that  the  angle  of  reflection  is  equal  to  the  angle 
of  incidence. 

Catoptric  Test  (kat-op'-trik).  A  test  for  cataract 
by  light  reflected  from  the  crystalline  lens.  In 
this  test  ask  the  patient  to  look  straight  ahead, 
then  hold  a  lighted  candfe  about  twelve  inches 
in  front  of  the  eye,  a  little  to  one  side,  while 
you  stand  slightly  on  the  other  and  look  into 
his  pupil.  If  there  is  no  opacity  of  the  lens  or 
capsule  you  will  notice  three  images  of  the  can- 


50  LEWIS  POCKET 

.  die.  The  first  will  be  on  the  surface  of  the 
cornea  in  an  upright  position,  the  second  will 
be  on  the  anterior  surface  of  the  lens,  also  up- 
right, while  the  third  will  be  inverted  and  much 
smaller  on  the  posterior  surface  of  the  lens,  but 
when  there  is  a  cataract  you  will  fail  to  find  the 
inverted  image   (known  as  Pyrkinges  Images). 

Catoptry  (kat-op'-tre).  The  unit  of  reflective 
power  of  curved  mirrors.  A  mirror  that  will 
reflect  parallel  rays  of  light  to  a  point  of  focus 
at  a  distance  of  one  meter. 

Cat's-eye  Pupil.  Where  the  pupil  of  the  eye  is 
long  and  narrow  (slit-like). 

Caustic  Curve  (kaus'-tik).  A  curve  to  which  the 
raj^s  of  light  reflected  or  refracted  by  another 
curve  are  tangent. 

Caustic  Surface.  A  surface  to  which  rays  of  light 
reflected  or  refracted  by  another  surface  are 
tangents.  Caustic  curves  are  called  catacaustic 
when  formed  by  reflection  and  diacaustic  when 
formed  by  refraction. 

Cellulitis  (sel-u-li'-tis).  Inflammation  of  the  loose 
tissues  of  the  orbit. 

Center  (of  curvature).  If  the  surface  of  a  lens 
were  completed  so  as  to  form  a  circle,  its  center 
would  be  the  center  of  curvature.  (See  Optical 
Center.) 

Centimeter  (sen'-tlm-e-ter).  One-hundredth  part 
of  a  meter. 

Centrad  (sen'-trad).  Toward  the  center;  unit  of 
measurement  for  prisms  which  will  produce  a 
deviation  in  a  ray  of  light  one-hundredth  of  a 
radian. 


OPHTHALMIC  DICTIONARY  51 

iLentric  (sen'-trik).    Pertaining  to  a  nerve  center. 
Centrifugal   (sen-trif'-u-gal).     Tending,  or  causing, 

to  recede  from  tlie  center. 
Centrifugal  Impression.   An  irnpression  sent  from 

a  nerve  center  outwards  to  a  muscle  or  muscles 

by  which  motion  is  produced. 
Centrophose.        (Gr.     kentron  =  center  +  phos  = 

light.)     A  subjective  sensation  of  a  light  spot  or 

patch,  the  cause  being  located  in  the  optic  brain 

center. 
Ceratitis  (ser-at-i'-tis).    (Gr.  "horn"  +  suffix,  itis  = 

inflammation.)     The  same  as  keratitis. 

Ceratonosus  (ser-at-on'-o-sus).  (Gr.  keras  = 
horn  +  nosos  =  disease.)  Any  disease  of  the 
cornea. 

Ceratotome  (se-rat'-o-tom).  A  knife  for  dividing 
the  cornea. 

Chalazion  (chal-a'-zi-on).  (Gr.  "Hail.")  A  tumor 
on  the  eyelid.  On  the  under  surface  of  the 
tarsal    plate   of   the   upper   and    lower   lid    are 

-  numerous  creases  or  depressions  running  at 
right  angles  to  the  margin  of  the  lid.  There 
are  about  thirty  of  them  in  the  upper  lid  and 
about  twenty  in  the  lower?  In  these  depres- 
sions are  small  tubular  glands,  called  meibomian 
glands,  and  their  ducts  open  next  to  the  margin 
of  the  lid.  A  chalazion  is  an  enlargement  of 
one  or  more  of  these  glands,  due  to  the  stop- 
page of  their  ducts,  and  is  usually  chronic  in 
character.  A  chalazion  is  also  called  a  tarsal 
tumor,  tarsal  cyst,  or  meibomian  cyst,  etc.  It  is 
not  a  true  retention  cyst,  but  its  contents  may 
soften  so  that  it  will  become  an  encysted 
abscesb.     At   first   its   contents   are   gelatinous, 


52  LEWIS  POCKET 

but  later  may  become  purulent.  The  tumor  is 
firm,  round,  with  the  skin  moving  freely  over 
the  mass,  but  it  is  firmly  attached  to  the  tarsal 
plate.  It  has  so  much  the  appearance  of  a  seba- 
ceous cyst  that  one  is  liable  to  be  mistaken  in 
the  diagnosis,  unless  he  is  familiar  with  the 
disease.  Usually  chalazion  tends  toward  the 
conjunctiva,  and,  if  the  lid  is  everted,  the  posi- 
tion of  the  tumor  may  be  located  by  a  bluish 
discoloration,  or,  if  the  contents  are  purulent, 
a  yellowish  discoloration.  The  primary  cause 
of  this  trouble  is  not  definitely  known,  but  a 
debilitated  condition  of  the  system,  eye-strain, 
and  blepharitis  marginalis  seem  to  be  the  fac- 
tors in  producing  chalazion. 

Chamber.  (Gr.  "vaulted  room.")  The  spaces  of 
the  eye.  A  term  used  in  speaking  of  the  eye, 
in  which  there  are  three  chambers.  The  an- 
terior c.  is  the  space  between  the  cornea  and 
the  front  surface  of  the  iris;  the  posterior  c, 
the  space  between  the  iris  and  the  front  sur- 
face of  the  lens  capsule.  These  two  are  filled 
with  the  aqueous  humor  and  communicates 
through  the  pupil;  vitreous  c,  the  space  sur- 
rounded by  the  hyaloid  membrane  behind  the 
lens,  occupying  four-fifths  of  the  globe  of  the 
eye. 

Chemosis  (ke-mo'-sis).  (Gr.  "an  aperture"  and 
suffix  osis,  signifying  "morbid  condition.")  A 
swollen  condition  of  the  conjunctiva,  forming 
an  elevated  ring  around  the  cornea. 

Chiasm  (ki'-asm).  (Gr.  chiasma  =  two  crossing 
lines.)  A  crossing;  especially  the  crossing  of 
the  fibers  of  the  optic  nerve  (optic  commissure). 


OPHTHALMIC  DICTIONARY  53 

Chiastometer  (ki-as-tom'-e-ter).  An  instrument 
for  ascertaining  the  deviation  of  the  optic  axis. 

Chlorophane  (klo'-ro-fan).  (Gr.  chloros  =  green- 
ish yellow  +  phaino  =  I  show).  A  green-yellow 
pigment  from  the  retina. 

Chloropsia.  (Gr.  chloros  =  yellowish  green  + 
opsis  =  eyesight).  Green  vision.  A  condition 
in  which  all  objects  appear  to  be  colored  green. 

Choked  Disc.  Congested  arid  inflamed  state  of 
the  optic  disc. 

Chondral  (kon'-dral).  (Gr.  chondros  =  cartilage.) 
Pertaining  to  cartilage. 

Chorea  (ko-re'-ah).  (Gr.  choreia  =  choral  dance.) 
St.  Vitus'  dance.  A  disease  of  the  nervous  sys- 
tem, characterized  by  a  succession  of  irregular, 
clonic  involuntary  movements,  of  limited  range 
occurring  in  almost  all  parts  of  the  body.  Con- 
trol of  the  muscles  is  not  lost,  but  voluntary 
motions  are  interfered  with  by  the  involuntary 
contractions. 

Chorioid.   See  Choroid. 

Choroid  (ko'-roid).  "Skin-like  bag  with  multitude 
of  blood  vessels."  That  part  of  the  second  tunic 
of  the  eye  extending  from  the  optic  nerve  en- 
trance to  the  posterior  limit  of  the  ciliary  body. 
It  is  covered  by  the  retina  on  the  inner  side. 
It  constitutes  the  posterior  two-thirds  of  this 
tascular  tunic.  Its  thickness  gradually  dimin- 
ishes toward  the  ciliary  body.  The  choroid 
consists  of  a  compact  mass  of  connective  tissue, 
stroma,  which  supports  the  numerous  blood 
vessels  of  varying  size;  forming  three  layers. 


54  LEWIS  POCKET 

1.  The  layer  of  stroma  containing  large  blood 
vessels. 

2.  The  chorio-capillaris. 

3.  The  membrana  vitrea. 

The  first  layer  is  the  most  conspicuous  of  the 
three,  for  its  large  blood  vessels  emerge  into 
four  main  trunks,  the  vena  vorticosae;  these 
pierce  the  sclerotic  at  equal  distances  apart, 
running  obliquely  backward.  The  nerves  of  the 
choroid  are  derived  from  branches  of  the  long 
and  short  ciliary  nerves.  Its  blood  supply  is 
fi-om  the  short  posterior,  long  posterior  and 
anterior  ciliary  arteries.  The  red  reflex  seen 
in  the  eye  when  viewed  with  the  retiiioscope 
and  ophthalmoscope  is  due  to  the  reddish  color 
of  the  blood  vessels  in  the  choroid  showing 
through  the  retina. 

Choroidal  Fissure.  The  opening  in  the  choroid 
through  which  the  optic  nerve  passes  to  form 
the  retina. 

Choroideremia  (ko-roi-de-re'-me-ah).  Absence  of 
the  choroid. 

Choroiditis  (ko-roi-di'-tis).  Inflammation  of  the 
choroid. 

Choroidocycli'tis.  Inflammation  of  the  choroid 
and  ciliary  processes. 

Choroidoiritis  (ko-roi-do-i-ri'-tis).  Inflammation  of 
the  choroid  and  iris. 

Choroidoretini'tis.  Inflammation  of  the  choroid 
and  retina. 

Chromatic  (kro-mat'-ik).  (Gr.  chroma  =  color.) 
Relating  to  color. 

Chromatic  Aberration.     See  Aberration. 


OPHTHALMIC  DICTIONARY  55 

Chromatodysopia  (kro-mat-o-dys-o'-pi-ah).  (Gr. 
chroma  ^  color  +  dys  ---=^  bad  +  ops  ==  eye.)  Col- 
or-blindness. 

''/hromatogenous  (kro-mat-oj'-en-us).  (Gr.  chroma 
=  color  +  gennao  =  I  produce.)  Producing  color. 

Chromatology  (kro-mat-ol'-o-gy).  The  study  of 
colors. 

Chromatom'eter.  An  instrument  for  measuring 
color  or  color  perception, 

Chromatophobia  (kro-mat-o-fo'-be-ah).  (Gr.  chro- 
ma =  color  +  phobos  =  fear.)  An  abnormal 
fear  of  color. 

Chromatopsia  (kro-mat-op'-se-ah).  (Gr.  chroma  = 
color  +  opsis  =  vision.)  Abnormal  sensation 
of  color,  due  to  disorders  of  the  optic  centers, 
or  to  drugs,  especially  santonin. 

Chromatoptometry  (kro-mat-op-tom'-et-ry).  Tak- 
ing the  measurement  of  the  power  of  color  per- 
ception. 

Chromometer  (kro-mom'-et-er).  An  instrument  for 
measuring  coloring  matter  present. 

Chromoptometer  (kro-mop^tom'-et-er).  An  instru- 
ment to  test  the  color  sense. 

Chromoscope.  (Gr.  chromo  =  color  +  skopeo  =  I 
view.)  An  apparatus  for  testing  the  color  sense. 

Cibisitome  (sib-is'-it-om).  An  instrument  for  in- 
cising the  lens  capsule. 

Cilia.  (L.  cilium  =  eyelash.)  The  eyelashes. 
Hair. 

Ciliariscope  (sil-i-ar'-is-cope).  An  instrument  for 
examining  the  ciliary  region  of  the  eye. 


nu 


LEWIS   POCKET 


Ciliary  (sil'-i-a-ry).  Pertaining  to,  or  like,  the  eye- 
lashes. 

Ciliary  Body.  The  middle  part  of  the  second  tunic, 
composed  of  ciliary  processes,  ciliary  veins, 
ciliary  muscles,  ciliary  nerves  and  arteries. 


Cut    showing   Choroid.    Ciliary    Body.    Iris   and    Xerves. 


Ciliary  Processes.  The  radiating  circular  folds 
composed  of  a  connective  tissue  stroma.' which 
pass  up  over  the  ciliary  body.  There  are  about 
sixty  or  seventy  in  number. 

Cillo  (cil'-lo)  or  Cillosis.  (Gr.  "I  move.")  A 
trembling  or  spasmodic  twitch  of  the  eyelids. 

Cinerea  (sin-e'-re-ah).  (L.  cinereus  =  ashy.)  The 
gray  matter  of  the  nervous  system. 

Circle  (sir'-kl).  (L.  circulus,  dim  of  circus.  Gr. 
kirkos — a  ring.)   A  plane  figure  whose  periphery 


OPHTHALMIC  DICTIONARY  57 

is    everywhere    equally    distant    from    a    point 
within  it,  the  center. 
Circles  of  Haller.     Venous  and  arterial  circles  of 
the  eye. 

Circulation  fo^r-cu-la'-shun).  (L.  circulare  =  to 
encompass.)  The  passage  of  blood  in  going 
from  and  returning  to  the  heart  after  having 
made  a  circuit  of  the  body. 

Circum.  (L.  around.)  A  prefix  denoting  a  circu- 
lar movement,  or  a  position  surrounding  the 
part  indicated  by  the  word  to  which  it  is  joined. 
Circumlental,  surrounding  the  crystalline  lens; 
circum  ocular,  around  the  eye;  circumorbital, 
around  the  orbit. 

Circumference  (ser-kum'-fe-rens).  (L.  circum  = 
around  +  ferre  =  to  bear.)  The  line  which 
bounds  a  circle. 

Clonic  Spasm.  (Gr.  commotion.)  An  intermittent 
involuntary  contraction  of  a  muscle,  which 
shows  itself  when  the  muscle  is  in  use. 

Cobalt.  A  hard,  brittle,  and  heavy  metal  whose 
compounds  afford  pigments.  The  Cobalt-blue 
test  glass  being  named  after  the  blue  pigment. 
Cobalt-Blue  Glass  contains  a  great  deal  of 
red,  and  allows  only  the  blue  and  red  rays  of 
the  spectrum  to  pass  through,  neutralizing  the 
other  five  colors  contained  in  white  light.  It 
is  used  in  testing  the  ametropia  when  the  pa- 
tient is  not  color  blind. 

Cocaine  (ko-ka'-in).  A  local  anaesthetic  and  mydri- 
atic. Cocaine  dilates  the  pupil,  and  hence  would 
seem  to  call  for  mention  in  this  place,  although, 
strictly  speaking,  it  does  not  belong  to  the 
mydriatics  proper — that  is,  the  dilatation  of  the 


58  LEWIS  POCKET 

pupil  by  cocaine  is  not  produced,  as  in  their 
case,  by  its  action  upon  the  contracting  or  the 
dilating  fibers  of  the  iris,  but  by  a  contraction  of 
the  blood  vessels  of  the  iris.  The  dilatation  of  the 
pupil  is  therefore  only  a  moderate  one,  and  the 
reaction  of  the  pupil  to  light  persists;  moreover, 
mydriatics  and  miotics  still  produce  an  effect. 
If  cocaine  is  instilled  into  an  eye  the  pupil  of 
which  has  been  dilated  by  atropine,  the  dilata- 
tion increases  somewhat  in  consequence  of  the 
anaemia  of  the  iris  which  then  ensues;  hence 
the  mydriasis  produced  by  the  simultaneous 
action  of  atropine  and  cocaine  is  the  most  com- 
plete that  can  possibly  be  attained.  The  ac- 
commodation is  not  paralyzed  by  cocaine,  but 
only  somewhat  weakened. 

Cohesion  (ko-he'-shun).  (L.  con  =  together + 
haereo  =  to  stick.)  That  form  of  attraction  by 
which  the  particles  of  a  body  are  united 
throughout  the  mass,  whether  like  or  unlike. 

Colmascope  (cor-ma-scope).  An  instrument  for 
the  detection  of  strains  and  stresses  in  lenses, 
either  mounted  or  unmounted,  as  a  result  of 
undue  tightening  of  screws  or  imperfections  in 
manufacture. 

Collyrium  (col-lyr'-i-um).  (Gr.  kollyrion  =  an 
eyewater.)    Any  lotion  to  be  dropped  in  the  eye. 

Coloboma  (kol-o-bo'-mah).  (Gr.  koloboma  :=  an 
imperfection.)  A  tear  or  break  in  the  eyeball, 
as  in  the  iris  or  choroid. 

Color-Blindness  (Achromatopsia).  Blindness  for 
one  or  more  colors.  Due  to  the  absence  from 
the  retina  of  one  or  two  of  the  three  primary 
substances   (according  to  Hering).     The  test  is 


OPHTHALMIC  DICTIONARY  59 

liiade  by  presenting  the  patient  with  samples  of 
different  colored  yarns — a  number  of  each  color, 
but  different  shades — and  the  patient  is  re- 
quested to  separate  them.  Persons  having  this 
anomaly  of  vision  are  generally  unaware  of  it 
themselves. 

Commissure  (kom'-mis-ur).  (Optic.)  (L.  com- 
mittere,  "to  unite.")  The  x-like  crossing  of  the 
optic  nerves. 

Composite  Number  (kom-poz'-it).  (L.  com  =  to- 
gether -f-  ponere  =  to  put.)  A  number  which 
can  be  exactly  divided  by  a  number  exceeding 
unity. 

Compound  Lens.  A  lens  that  contains  a  sphere 
and  8.  cylinder. 

Com  us  (ko'-mus).  A  cone.  A  crescentic  patch  of 
atrophic  choroid  tissue  near  the  optic  papilla  in 
myopia. 

Concave.  (L.  concavus  =  hollow.)  Hollow  and 
curved  or  rounded.     The  opposite  to  convex. 

Concavo-convex.  Concave  on  one  side  and  convex 
on  the  other.  If  the  convexity  exceeds  the  con- 
cavity it  is  known  as  a  periscopic  convex  lens. 
If  the  concavity  exceeds  the  convexity  it  is 
known  as  a  periscopic  concave  lens. 

Concentric  (kon-sen'-tric).  (L.  con  ==  together -f- 
centrum  =  center.)  That  which  has  a  common 
center  with. something  else. 

Concentrlcal  (tri-kal).  Having  a  common  center, 
as  circles  of  different  size,  one  within  another. 

Concomitant  (kon-com'-it-ant).  (L.  concomitare  = 
to  accompany.)  Accompanying.  Concomitant 
Squint  is  a  condition  where  the  two  eyes  devi- 


60  LEWIS  POCKET 

ate,  but  accompany  one  another  in  their  move- 
ment. The  object  can  be  seen  by  either  eye, 
but  not  the  two  eyes  at  the  same  time. 

Cone  (kon).  (Gr.  konos  =  peg.)  The  elementary 
form  considered  in  arithmetic  is  a  solid  gen- 
erated by  the  revolution  of  a  right-angled  tri- 
angle about  one  of  its  sides  as  an  axis. 

Cone  Muscle  Test.  This  consists  of  a  cone 
cemented  to  a  ground  glass  disc,  and  is  used  as 
follows:  It  is  inserted  into  one  cell  of  trial 
frame  in  front  of  the  correction  for  the  ametro- 
pia, which  must  be  properly  centered  as  to 
pupillary  distance,  and  a  solid  blank  disc  is  put 
into  the  cell  in  front  of  the  other  eye.  •  The 
patient's  attention  is  then  directed  to  a  light 
(preferably  a  candle  or  small  gas  light)  twenty 
feet  away;  and  the  action  of  the  cone  is  such 
that  the  light  will  resolve  itself  into  a  circle  of 
light.  The  other  eye  is  then  uncovered,  and  if 
there  is  no  muscular  error  the  light  will  appear 
in  the  center  of  the  circle.  If  there  is  muscular 
error  the  light  will  be  either  above  or  below  or 
to  one  side  of  center,  and  can  be  brought  to 
center  by  the  proper  prism  with  base  in  proper 
position.  This  does  away  with  necessity  for 
computations  where  there  is  combined  prismatic 
error  in  different  angles,  and  gives  at  once  the 
position  of  the  base  of  the  correcting  prism. 
(See  Muscular  Imbalance.) 

Conical  (con'-ic-al).  That  which  is  round  and 
tapering  to  a  point. 

Conical  Cornea.  A  cone-like  protrusion  of  the 
cornea  anteriorly  due  to  increased  intraocular 
pressure  and  weakening  of  its  central  portion. 


OPHTHALMIC  DICTIONARY  61 

Many  forms  of  operations  have  been  suggested 
and  while  some  have  been  of  slight  benefit,  no 
complete  cure  is  known.  Vision  can  usually  be 
improved  by  means  of  an  opaque  disc  with  an 
opening  in  its  center  and  worn  as  an  eye  glass. 
(Same  as  Keratoconus.) 

Conjugate.  (L.  con  =  with -f  jugare  =  to  join.) 
Coupled.     To  yoke  together. 

Conjugate  Deviation.  The  deviation  of  both  eyes 
in  the  same  direction. 

Conjugate  Foci  (kon'-ju-gat).  Two  points  so  situ- 
ated in  relation  to  each  other  that  the  direction 
of  a  ray  proceeding  from  either  of  them,  after 
reflection  or  refraction,  passes  through  the 
other.  Secondary  c.  A  conjugate  foci  formed 
on  a  secondary  axis. 

Conjunctiva  (kon-junc-ti'-va).  (L,  con  =  with + 
jungere  =  to  join  together.)  The  mucous  mem- 
brane of  the  eye.  It  covers  the  anterior  sur- 
face of  the  eye,  passing  backward  about  one- 
half  inch,  where  it  turns  (fornix)  to  line  the 
inner  surface  of  the  eyelids,  thus  forming  a 
complete  sac  when  the  eyelids  are  closed.  It 
consists  of  two  portions;  the  ocular  portion, 
which  covers  the  sclerotic,  and  the  palpebral 
portion,  which  lines  the  inner  surface  of  the 
lids.  The  ocular  portion  is  loosely  connected 
with  the  sclerotic,  but  firmly  attached  to  the 
edge  (limbus)  of  the  cornea.  The  palpebral 
portion  is  thick,  opaque,  highly  vascular,  and 
covered  with  numerous  papillae.  At  the  margin 
of  the  lids,  it  becomes  continuous  with  the  lin- 

•  ing  membrane  of  the  ducts  of  the  meibomian 
glands.    At  its  outer  and  upper  angle  there  are 


62  LEWIS  POCKET 

from  seven  to  ten  ducts  through  which  the  tears 
pass  from  the  lacrimal  glands.  It  receives  its 
blood  supply  from  the  palpebral  and  lacrimal 
arteries.  Its  vein,  the  post-tarsal,  is  tributary  to 
the  ophthalmic  vein.  It  receives  its  nerve  sup- 
ply from  the  fifth  pair  entering  at  the  inner  and 
outer  angle  of  the  orbit. 

Conjunctivitis  (kon-junc-tiv-i'-tis).  Inflammation 
of  the  conjunctiva. 

Convergence  (kon-ver'-gence).  (L.  con  =  with  + 
vergere  =  to  turn.)  The  act  or  power  of  turn- 
ing the  eyes  from  their  position  of  rest. 
When  the  eyes  are  emmetropic  and  ortho- 
phoric,  the  two  functions,  accommodation  and 
convergence,  work  together,  yet  their  objects 
are  totally  different,  but  their  harmonious  co- 
operation is  none  the  less  essential.  The  func- 
tion of  accommodation  is  the  focusing  of  the 
rays  of  light,  on  the  retina  of  each  eye  singly, 
which  come  from  objects  looked  at  within  20 
feet  from  the  eye;  while  the  function  of  con- 
vergence is  the  turning  of  the  eye  so  that  the 
image  of  the  object  looked  at  will  fall  on  corre- 
sponding parts  of  the  retina  in  each  eye.  For  a 
pair  of  normal  eyes  to  view  an  object  at  a  given 
distance  the  same  amount  of  accommodation 
and  convergence  will  be  required.  For  in- 
stance, to  view  an  object  at  13  inches,  it  will  be 
necessary  'to  use  three  dioptrics  of  accommo- 
dation and  three  meter  angles  of  convergence, 
and  if  the  object  was  brought  nearer,  the  accom- 
modation and  convergence  would  increase  an 
equal  amount.  The  same  nerve  (third  or  motor 
oculi)  supplies  the  muscles  that  perform  both 
functions.   Turning  the  eyes  outward  from  their 


OPHTHALMIC  DICTIONARY  63 

position  of  rest  is  called  negative  convergence, 
or  abduction;  turning  the  eyes  inward  from 
their  position  of  rest  is  called  positive  converg- 
ence, or  adduction.  The  number  of  degrees  of 
convergence  that  can  be  used  without  changing 
the  accommodation  is  called  relative  converg- 
ence. The  total  amount  one  has,  the  Amplitude. 
Converge.    Directed  toward  the  same  point. 

Convex.  That  which  has  a  rounded  and  elevated 
surface.  The  surface,  if  continued  at  the  same 
radius  of  curvature,  would  form  a  complete 
circle,  or  sphere. 

Convexo-concave.  Convex  on  one  side  and  con- 
cave on  the  other.  If  the  convexity  exceeds  the 
concavity  it  is  known  as  a  periscopic  convex 
lens.  If  the  concavity  exceeds  the  convexity  it 
is  known  as  a  periscopic  concave  lens. 

Copiopia  (kop-i-o'-pi-ah).  (Gr.  kopos  =  fatigue  + 
ops  =  eye.)  A  worn-out  state  of  the  eye,  caused 
by  eye-strain. 

Coquille-Plano  Lenses  (plus  8D.  on  one  side  and 
minus  8D.  on  the  other).  MiCoquille  are  plus 
4D.  on  one  side  and  minus  4D.  on  the  other. 
They  are  nearly  always  colored. 

Cored  Isis  (kor-ek'-lis-is).  (Gr.  kore  =  pupil + 
kleisis  =  closure.)  That  condition  in  which  the 
pupil  of  the  eye  is  obliterated. 

Corectasis  (kor-ek'-tas-is).     Dilatation  of  the  pupil. 

Corectome  (kor-ec'-to-me).  An  instrument  used  in 
cutting  for  iridectomy. 

Corectomy  (ko-rek'-to-me).  (Gr.  kore  =  pupil -f 
ektome  =  excision.)     See  Iridectomy. 

Tiorectopia   (kor-ec-to'-pi-ah).    (Gr.  kore  =  pupil  + 


64  LEWIS  POCKi^T 

ektopos  =  out    of    place.)       That    condition    in 
which  the  pupil  is  displaced. 

Coredialysis  (kor-e-di-al'-ys-is).  An  operation  in 
which  the  iris  is  detached  from  the  ciliary  liga- 
ment for  a  new  pupil. 

Corelysis  (ko-rel'-is-is).  (Gr.  kore  =  pupil  +  lysis 
=  a  loosening.)  The  loosening  of  adhesions  be- 
tween the  capsule  of  the  lens  and  the  iris. 

Coremorphosis  fkor-e-mor'-pho-sis).  (Gr.  kore  =^ 
pupil  -f  morphosis  =  formation.)  Creation  of  an 
artificial  pupil. 

Coreometer  (kor-e-om'-et-er).  (Gr.  kore  =  pupil  + 
metron  =  measure.)  A  contrivance  used  for 
measuring  the  pupil. 

Co  re  plasty  (Gr.  kore  =  pupil  +  plasso  =  I  form). 
An  operation  for  forming  an  artificial  pupil. 

Cornea  (kor'-ne-ah).  (L.  corneus  =  horn-like.) 
The  anterior  one-sixth  of  the  first  tunic  of  the 
eyeball.  It  is  transparent,  convex,  and  fitted 
into  the  sclerotic  like  a  watch  crystal,  having  a 
radius  of  7.8  mm.  on  its  anterior  surface  and  6.5 
mm.  on  the  posterior  surface.  It  has  a  vertical 
diameter  of  about  11  mm.  and  the  horizontal 
diameter  is  12  mm.  In  thickness  it  is  about  1 
mm.  at  the  center,  while  at  the  periphery  it  is 
1.12  mm.  The  cornea  has  no  blood-vessels  ex- 
cept for  a  narrow  space  about  1  mm.  wide  at 
the  margin,  derived  from  the  anterior  ciliary 
arteries.  The  venous  roots  become  tributaries 
of  the  anterior  ciliary  vein.  The  cornea  is  well 
supplied  with  nerves  and  lymphatics.  It  serves  to 
transmit  light  into  the  eye,  and  next  to  the  layer 
of  tears  becomes  the  first  refracting  medium.  It 
is  convex  in  front  and  concave  behind.    Its  curv- 


OPHTHALMIC  DICTIONARY  65 

atiire  varies  in  different  individuals.  It  is  com- 
posed of  five  layers,  arranged  as  follows,  from 
without  inward,  namely:  (1)  Conjunctiva  epi- 
thelium; (2)  Bowman's  membrane;  (3)  Cornea 
proper;  (4)  Membrane  Descemet;  (5)  Endothe- 
lium. The  first  layer  (conjunctiva  epithelium) 
serves  to  protect  the  nerves  in  Bowman's  mem- 
brane from  cold,  wind,  and  dust,  and  at  the 
same  time  gives  a  highly  polished  surface  to  the 
cornea.  The  second  layer  (Bowman's  mem- 
brane) is  a  layer  of  sensitive  nerves  and  elastic 
tissue,  and  protects  the  cornea  proper  on  the 
anterior  side,  and  at  the  same  time  gives  the 
cornea  an  elastic  nature.  The  third  layer  (cor- 
nea proper)  is  the  foundation  layer  of  the  cor- 
nea. It  is  composed  of  a  horn-like  substance 
and  is  non-sensitive  and  merely  serves  to  keep 
the  cornea  in  shape.  The  fourth  layer  (Mem- 
brane Descemet)  is  a  layer  similar  to  Bowman's 
membrane,  and  protects  the  cornea  proper  from 
any  diseased  condition  from  the  posterior  side. 
The  fifth  layer  (endothelium)  is  a  lining  mem- 
brane which  separates  the  aqueous  humor  from 
the  fourth  layer,  and  at  the  same  time  forms  a 
sort  of  sac  which  contains  the  aqueous  humor. 
The  cornea  has  an  index  of  refraction  of  1.33. 
Its  nerve  supply  arises  from  the  ciliary  nerves. 

Cor'neal.   Pertaining  to  the  cornea. 

Corneal  Astigmatism.     See  Astigmatism. 

Corneal    Facets    (fas'-ets).     Small,    plain,   distinct 
surfaces  of  the  cornea. 

Corneitis   (cor-ne-i'-tis).    inflammation  of  the  cor- 
nea. 

Corneo-iritis.   Inflammation  of  the  iris  and  cornea. 


Corneosciera.  The  cornea  and  sclera  taken  to- 
gether, forming  the  external  coaling  of  the 
eyeball. 

Corradiation  (kor-ra'-di-a'-shun).  A  conjunction  or 
concentration  of  rays  in  one  point. 

Correction.  Making  good  an  abnormal  condition, 
such  as  correcting  an  error  of  refraction. 

Cortical  (kor'-tik-al).  (L.  cortex  =  bark.)  To  be 
near  the  border.  Cortical  Cataract  is  that  vari- 
ety in  which  the  opacity  begins  at  the  border  of 
the  crystalline  lens  and  gradually  spreads 
toward  the  center,  which  it  sooner  or  later 
involves. 

Cosecant  (ko-se'-kant).  The  secant  of  the  comple- 
ment of  an  arc  or  angle. 

Cosine  (ko'-sin).  The  sine  of  the  complement  of 
an  arc  or  angle. 

Cotangent  (ko-tan'-jent).  The  tangent  of  the  com- 
plement of  an  arc  or  angle. 

Couching.  That  condition  in  which  the  lens  is 
displaced  in  cataract.  This  operation  is  now 
obsolete. 

Coversed  Sine  (ko-versf  sine).  The  versed  sine 
of  the  complement  of  an  arc  or  angle. 

Cover  Test.  A  test  for  muscular  imbalance  by 
covering  one  eye  and  observing  its  movement 
while  uncovering,  the  point  of  fixation  being 
established. 

Cramp.   A  spasmodic  muscular  contraction. 

Cribriform  (krib'-ri-form).  (L.  cribrum  =  sieve -h 
forma  =  form.)    Perforated  like  a  sieve. 

Critical  Angle  (krit'-ik-al).  The  least  angle  of  in- 
cidence at  which  a  ray  of  light  traveling  in  a 


OPHTHALMIC  DICTIONARY  67 

denser  medium  is  totally  reflected  at  the  sur- 
face which  separates  it  from  a  rarer  medium; 
also  known  as  limit  angle.  The  limit  angle  of 
crown  glass  is  40°  49';  that  of  flint  glass,  37°  36'. 

Crossed  Diplopia.     See  Diplopia. 

Crystalline  (Gr.  "crystal").  Clear,  transparent. 
Resembling  or  of  the  nature 'of  crystal. 

Crystalline  Lens  (krys'-tal-lin).  The  lens  of  the 
eye,  which  resembles  a  crystal.  It  is  a  bi- 
convexed,  transparent,  elastic  body  having  a 
diameter  of  about  8.5  mm.  and  its  axial  thick- 
ness about  3.6  mm.  It  has  a  radius  of  curvature 
on  the  anterior  surface  of  10  mm.,  and  that  of 
the  posterior  surface  6  mm,,  while  the  eye  is  in 
a  state  of  rest.  It  is  located  in  the  hyaloid  fossa 
of  the  vitreous,  just  behind  the  pupil,  and  is 
made  up  of  layers  like  an  onion,  which  gives  it 
an  elastic  nature.  The  lens  itself  is  enclosed  in 
the  lens  capsule,  which  is  held  in  position  by 
the  suspensory  ligaments.  Its  index  of  refrac- 
tion is  1.43,  and  it  represents  from  16  to  19  diop- 
tries  of  plus  when  the  eye  is  at  rest. 

Crytometer.     See  Curtometer. 

Cube  (kub).  (Gr.  kubos  =^  a  die,  a  cube.)  (a)  A 
regular  solid  with  Kix  square  faces;  (b)  to  raise 
to  the  third  power;  (c)  the  third  power  of  a 
number. 

Cube  Root.  The  cube  root  of  a  perfect  third  power 
is  one  of  the  three  equal  factors  of  that  power. 
A  number  which  has  not  a  perfect  third  power 
has  not  three  equal  factors. 

Cuneus  (cu'-ne-us).  (L.  wedge.)  The  wedge-shaped 
portion  of  the  occipital  lobe  of  the  cerebrum, 
situated    between    the    occipital    and    calcarine 


68  LEWIS  POCKET 

fissures.    The  cuneus  receives  the  cortical  ter- 
mini of  the  optic  tract. 


Cupped  Disc.  That  condition  in  which  the  optic 
disc  has  become  cupped,  as  seen  in  glaucoma. 

Curtom'eter.  An  instrument  for  measuring  curved 
surfaces. 

Curvature  (curv'-a-ture).  The  bending  of  a  line 
without  forming  angles. 

Cutaneous   (ku-ta'-ne-us).    Pertaining  to  the  skin. 

Cyclitis  (cyc-li'-tis).  (Gr.  kyklos  =  circle -f  itis  = 
inflammation.)  Inflammation  of  the  ciliary 
body. 

Cyclochoroiditis  (si-klo-ko-roid-i'-tis).  Inflamma- 
tion of  the  choroid  e.nd  ciliary  body. 

Cycloid  (si-kloyd).  Like  a  circle. 

Cyclophoria  (cyc-lo-fo'-ri-ah).    (Gr.  kyklos  ==  circle 


OPHTHALMIC  DICTIONARY  69 

+  phora  =  movement.)  That  condition  in  which 
the  vertical  axis  of  the  eye  inclines  to  the  right 
or  left  instead  of  standing  vertically,  the  extrin- 
sic muscles  being  at  rest. 

Cyclopia  (si-klo'-pe-ah).  (Gr.  kyklos  =  circle -f 
ops  =  eye.)    A  single  eye  in  center  of  forehead. 

Cycloplegia  (cy-clo-ple'-gi-ah).  (Gr.  kyklos  =  cir- 
cle +  plege  =  stroke.)  Paralysis  of  the  ciliary 
muscles. 

Cycloplegic.  A  drug  which  produces  paralysis  of 
the  ciliary  muscles  or  muscles  of  accommoda- 
tion 

Cyclot'omy  (Gr.  kyklos  =  circle  +  tome  =  inci- 
sion). Operation  of  cutting  the  ciliary  body  of 
the  eye. 

Cyclotropia  (Gr.  kyklos  =  circle -f  trope  =  turn). 
The  actual  turning  of  an  eye  on  its  optic  axis. 

Cylinder  (cyl'-in-der).  (Gr.  kylindros  =  a  roll.) 
See  Lens. 

Cylindrical.  Relating  to  or  the  shape  of  a  cylinder. 

Cyst  (sist).  (Gr.  kystis  =  bladder.)  Any  sac  con- 
taining a  liquid.  Dermoid  cyst  is  congenital. 
It  is  a  painless,  uninflammed  spheroidal  mass, 
situated  generally  at  the  outer  angle  of  the 
orbit,  on  a  level  with  the  outer  end  of  the  eye- 
.  brow. 

Cystitome  (sis'-tit-om).  An  instrument  used  for 
opening  the  sac  of  the  crystalline  lens. 

Cystot'omy  (Gr.  kystis  =  bladder  -f  tome  =  inci- 
sion). Incision  of  the  capsule  of  the  Crystalline 
Lens. 


70  LEWIS  POCKET 


D 


•  Abbreviation  for  dioptry,  dexter,  or  dose. 
Dacryadenalgia    (dak-ry-ad-en-ar-gi-ah).     (Gr.   dak- 
ryon  =  tear  +  aden  =  gland  +  algos  =  pain.) 
Pain  in  a  lacrimal  gland. 

Dacryagogue  (dak'-ry-ag-og).  (Gr.  dakryon  =  tear 
+  agogos  =  leader.)  A  medicine  which  causes 
a  flow  of  tears. 

Dacryoadenitis  (dak-ry-o-ad-en-i'-tis).  (Gr.  dak- 
ryon =  tear  +  aden  =  gland  +  itis.)  Inflamma- 
tion of  a  lacrimal  gland. 

Dacryocele  (dak'-ry-o-cele).  (Gr.  dakryon  ==  tear 
+  kele  =  hernia.)  A  protrusion  of  the  lacrimal 
sac. 

Dacryocyst  (dak'-ry-o-cyst).  (Gr.  dakryon  =  tear 
-f-  kystis  =  sac.)    The  tear  sac. 

Dacryocystalgia  (dak-ry-o-cyst-al'-gi-ah).  (Gr.  dak- 
ryon =  tear  +  kystis  ^  sac  -f-  algos  =  pain.) 
Pain  in  the  lacrimal  sac. 

Dacryocystitis  (dak-ry-o-cys-ti'-tis).  Inflammation 
of  the  lacrimal  sac. 

Dac'ryoid.   Resembling  a  tear. 

Dacryoma  (dak-ry-o'-ma).  (Gr.  dakryon  ^  tear, 
and  suffix  oma,  "morbid  state.")  A  lacrimal 
tumor  which  causes  an  obstruction  of  the  lac- 
rimal puncta,  so  that  the  tears  flow  over  the 
lids  upon  the  cheek. 

Dacryon  (Gr.  "a  tear"). 

Dacryops  (dak'-re-ops).  (Gr.  dakryon  =  tear -f 
ops  =  eye.)  A  watery  eye.  Applied  to  a  swell- 
ing of  the  lacrimal  sac  or  one  of  its  ducts. 

Dacryorrhea  (Gr.  dakryon  =  tear  +  rhoia  =  flow). 
Excessive  or  morbid  flow  of  tears. 


OPHTHALMIC  DICTIONARY  71 

Dacryopyorrhea      (Gr.     dakryon  =  tear  +  pyon  = 

pus  +  rhoia  =  flow).  Discharge  of  pus  from  the 

lacrimal  duct. 
Dacryopyo'sis      (Gr.      dakryon  =  tear  +  pyosis  = 

suppuration).   A  discharge  of  tears  mixed  with 

purulent  matter. 

Daltonism   (dawl'-ton-izm).    Color-blindness. 

Day-blindness  (day-blind'-ness).  Partially  blind  by 
day,  with  better  vision  at  night.  See  Hemera- 
lopia. 

Decameter  (dek'-a-me-ter).   Ten  meters. 

Decentered  (de-cen'-terd)  Lens.  A  lens  with  its 
optical  center  to  one  side  or  above  or  below  the 
center. 


Decentered   Lenses. 

Decentering  of  Lenses.  Instead  of  having  a  prism 
and  a  lens  combined,  where  you  wish  to  obtain 
the  effect  of  both,  it  is  possible  to  get  the  same 
result  by  simply  decentering  the  optical  center 
of  the  lens.  The  optical  center  of  a  plus  lens 
is  at  the  thickest  part,  and  in  the  minus  at  its 
thinnest  part,  while  the  geometrical  center  of  a 
lens  is  the  point  midway  between  all  edges.  A 
1-dioptry  lens  decentered  10  mm.  will  give  the 
effect  of  a  1°  prism,  while  a  2-D.  lens  will  only 
require  to  be  decentered  half  this  amount,  or 
5  mm. ;  a  3-D.  lens,  one-third  of  this  amount,  for 
the  same  effect,  and  so  on  according  to  the 
strength  of  the  lens.    To  obtain  the  effect  of  a 


2°  prism  these  lenses  must  be  decentered  twice 
as  much — that  is  to  say,  a  1-D.  lens,  20  mm.;  a 
2-D.  lens,  10  mm.;  a  3-D.,  6.3  mm.  From  this 
table  one  can  easily  figure  the  exact  amount 
any  lens  should  be  decentered  to  obtain  a  given 
prismatic  effect.  Law  of  Decentration:  Any 
lens  is  capable  of  producing  as  many  prism 
dioptrics  as  the  lens  possesses  dioptrics  of  re 
fraction,  provided  it  is  decentered  1  cm. — Pren- 
tice, Archives  of  Ophthalmology,  Vol.  XIX,  No.  ] 
and  No.  2,  New  York,  1890. 

Decentration  (de-cen-tra'-tion).  The  act  of  re- 
moving from  a  center. 

Decimal  (desM-mal).  (L.  decern  =  ten.)  Pertain- 
ing to  ten. 

Decimeter  (des'-i-me-ter).   One-tenth  of  a  meter. 

Decomposition  of  Light.  If  parallel  rays  of  sun- 
light pass  through  a  prism  it  is  not  only  re- 
fracted but  it  is  also  decomposed  into  its  vari- 
ous colors.  This  is  due  to  the  unequal  refrangi- 
bility  of  the  different  colored  rays  which  form 
white  light,  the  violet  being  refracted  the  most 
and  the  red  the  least,  thus  forming  the  spec- 
trum. 

Decussation  (de-ku-sa'-shon).  (L.  decussare  =  to 
cross.)  The  act  of  crossing  or  intersecting;  the 
crossing  of  two  lines,  rays,  fibers  of  nerves,  etc. 
Through  the  decussation  of  the  rays  in  the 
pupil  of  the  eye  the  image  of  the  object  on  the 
retina  is  inverted. 

Defect  (de-fecf).  A  departure  from  the  normal. 
When  speaking  of  defects  of  vision  we  mean 
the  visual  power  of  the  eye  is  not  normal. 


OPHTHALMIC  DICTIONARY  73 

Defining  Power,  Definition.  The  power  of  a  lens 
to  give  a  clear  outline. 

Denominator  (de-nom'-i-na-tor).  (L.  denominare  = 
to  name.)  (Arith.)  That  number  placed  below 
the  line  in  fractions  which  shows  into  how  many- 
parts  the  unit  is  divided.  (Alg.)  That  part  of 
any  expression  under  a  fractional  form  which  is 
situated  below  the  horizontal  line  signifying 
division. 

Deor'sumvergens  (L.  deorsum  =  downward  +  ver- 
gere  =  to  incline).  Dowmward  turning  of  the 
eye. 

Depilation  (dep-il-a'-shun).  (L.  de  ^=  from -|- pilus 
=  hair.)    The  removal  or  loss  of  the  hair. 

Deplumation  (de-plu-ma'-shun).  (L.  de  =  from + 
pluma  =  feather.)    Loss  of  eyelashes  by  disease. 

Deprimens  Oculi  (dep'-ri-mens  ok'-u-li).  (L.  depri- 
mere  =  to  depress.)    The  rectus  inferior  muscle. 

Descemet's  iVIembrane  (des-ce-mets'  mem'-brane). 
The  fourth  layer  of  the  cornea.    See  Cornea. 

Descemetitis  (des-em-e-ti'-tis).  Inflammation  of 
Descemet's  Membrane. 

Deviation  (de-vi-a'-shun).  (L.  de  =  from  +  via  = 
way.)  Turning  aside,  as  in  strabismus.  Conju- 
gate d.,  deviation  of  both  eyes  to  the  same  side. 
IVIinimum  d.,  the  smallest  deviation  of  a  ray 
that  a  given  prism  can  produce. 

Dexter,  Dextra   (dex'-ter,  dex'-tra).    On  right  side. 

Dextrad  (dex'-trad).  (L.  dexter  =  right.)  Toward 
the  right  side. 

Dextrophoria  (deks'-tro-phor'-ia).  (L.  dexter  = 
right  +  Gr.    phoria  =  tending.)     That    condition 


in  which  the  eyes  turn  to  the  right  when  the 
extrinsic  muscles  are  in  a  state  of  rest. 

Diacaustic  (di'-a-kas'-tik).  A  curve  formed  by  the 
consecutive  intersections  of  rays  of  light  re- 
fracted through  a  lens,  and  when  reflected  it  is 
called  catacaustic. 

Diagonal  (di-ag'-o-nal).  (Gr.  dia  =  through + 
gonia  =  comer,  angle.)  A  line  through  the  an- 
gles of  a  figure,  but  not  lying  in  its  sides  or 
faces. 

Diameter  (Gr.  diametros;  dia  =  through  +  metron 
=  measure).  A  straight  line  joining  opposite 
points  of  a  circle,  drawn  through  the  center. 

Diaphaneity  (di-af-a-ne'-i-ty).  Transparency;  the 
power  of  transmitting  light. 

Diaphanous  (di-af'-a-nous).  Having  power  to  trans- 
mit rays  of  light,  as  glass. 

Diaphragm  (di'-a-fram).  (Gr.  diaphragma  =  a 
partition  wall.)  A  term  applied  to  the  partition 
with  a  central  aperture  in  optical  instruments 
so  that  rays  of  light  may  be  controlled.  The  iris 
with  its  pupil  constitutes  the  diaphragm  of  the 
eye. 

Diapyesis  (di-ap-i-e'-sis).    Suppuration. 

Diffraction  (dif-frak'-shun).  (L.  diffractus;  diffrin- 
gere  =  to  break  up.)  Deflection  or  decomposi- 
tion of  light  in  passing  by  the  edges  of  opaque 
bodies  or  through  small  apertures. 

Diffusion  (dif-fu'-shun).  n.  (Optics)  A  spreading  or 
scattering  of  rays  of  light,  causing  a  blurred 
image  by  imperfect  refraction. 

Digit  (dij'-it).  (L.  digitus  =  finger.)  The  number 
represented  by  any  one  of  the  ten  symbols  0,  1, 


OPHTHALMIC  DICTIONARY  75 

2, 9.   The  term  is  more  often  used  to  desig- 
nate one  of  the  ten  sj^mbols  mentioned. 

Dilatant.   A  medicine  that  causes  dilatation. 
Dilatation    (di-la-ta'-shun).     (L.    dilatare  =  to    ex- 
pand.)   The  expansion  of  any  orifice  or  canal. 

Dilator  (di-la'-tor).  Dilator  iris  refers  to  the  radiat- 
ing fiber  of  the  iris  which  dilates  the  pupil. 

Diopter  (di-op'-ter).  (Gr.  dia  =  through  +  opsomai 
=  I  shall  see.)  A  leveling  instrument  of  ancient 
times,  equipped  with  sights  at  both  ends  and  a 
water  level  in  its  center.  The  theodolite,  by 
Hipparchus,  the  ancient  Greek  mathematician. 

Dioptometer  (di-op-tom'-e-ter).  An  instrument  for 
testing  ocular  refraction. 

Dioptometry  (di-op-tom'-e-tre).  The  measurement 
of  ocular  accommodation  and  refraction. 

Dioptral,  a.  Applied  to  the  refractive  power  of 
ophthalmic  lenses  numbered  according  to  the 
metric  system,  and  in  which  the  unit  of  power 
has  a  focal  length  of  1  meter.  Thus,  a  1-dioptry 
lens  is  specifically  a  member  of  the  dioptral 
system,  whereas  a  40-inch  telescope  lens  is  a 
member  of  a  dioptric  system. 

Dioptric  (di-op'-tric).    See  Dioptry, 

Dioptrical  (di-op'-tri-kal).  Of  or  pertaining  to 
dioptric. 

Dioptrics  (di-op'-trics).  That  branch  of  optics 
which  treats  of  the  refraction  of  light  by  any 
transparent  media,  as  air,  water,  or  glass. 

Dioptron  (di-op'-tron).  (Surg.)  A  dilating  specu- 
lum. 

Dioptry,  n.  (di-op'-tri).  (Gr.  dia  =  through  +  opso- 
mai =  I  shall  see.)    The  unit  for  expressing  the 


76  LEWIS  POCKET 

refractive  power  of  a  lens.  The  refractive  power 
of  a  lens  which  will  focus  parallel  rays  of  light 
at  a  distance  of  1  meter.  A  lens  of  2  dioptries 
f 2  D.)  has  a  focal  length  of  i  meter.  Synonyms: 
Dioptre,  Dioptric.    See  Focus. 

Diplocoria  (dip-lo-ko'-re-ah).  (Gr.  diplous  =  dou- 
ble -j-  kore  =  pupil.)    Double  pupil. 

Diplopia  (dip-lo'-pe-ah).  (Gr.  diplous  =  double  -|- 
opsis  =  vision.)  Double  vision;  seeing  one  ob- 
ject as  two.  The  object  of  convergence  is  to 
direct  the  yellow  spot  (or  macula  lutea)  in  each 
eye  toward  the  same  point,  so  as  to  obtain 
single  vision;  diplopia,  or  double  vision,  at  once 
resulting  when  the  image  of  an  object  falls  on 
parts  of  the  retina  which  do  not  exactly  corre- 
spond in  the  two  eyes. 

Binocular  d.,  double  vision  only  when  the  two 
eyes  are  exposed  to  view.  Heteronymous  d., 
where  the  object  seen  with  the  right  eye  ap- 
pears on  the  left  side,  and  that  of  the  left  eye 
on  the  right  side.  Homonymous  d.,  where  the 
object  of  the  right  eye  appears  on  the  right  side 
and  the  object  of  the  left  eye  on  the  left  side. 
Monocular  d.,  diplopia  with  a  single  eye. 

DIplopiometer  (dip-lo-pi-om'-e-ter).  An  instrument 
for  measuring  diplopia. 

Disc  (disk).  A  round  body  which  resembles  a 
small  circular  plate.  Optic  d.,  a  whitish  circular 
spot  in  the  retina  representing  the  entrance  of 
the  optic  nerve  into  the  globe  of  the  eye. 

Discission  (dis-ish'-un).  (L.  discindere  =  to  split.) 
The  rupture  of  the  capsule  of  the  crystalline 
lens  in  the  operation  for  soft  cataract. 

Diseases  of  the  Eye.    The  diseases  of  the  eye  are 


OPHTHALMIC  DICTIONARY  77 

many,  but  nearly  all  of  them  can  be  directly  or 
indirectly  attributed  to  eye-strain  or  impurity 
of  the  blood.  First,  relieve  any  eye-strain  by 
glasses;  second,  keep  the  bowels  regular;  third, 
fresh  air  and  exercise.  When  the  patient  re- 
quires further  attention,  proper  treatment 
should  be  instituted. 

Disparate  Points  (dis'-par-at).  (L.  disparare  =  to 
separate.)  Points  on  the  two  retinae  upon  which 
light  does  not  produce  the  same  impression. 

Disperse  (L.  dispersus;  dispergere  =  to  scatter 
about). 

Dispersing  Lens  (dis-per'-sing).  Same  as  concave 
lens. 

Dispersion  (dis-per'-shun).  The  process  of  scatter- 
ing the  rays  of  light  through  any  kind  of  a  lens. 

Distichiasis,  Distichia  (dis-te-ki'-a-sis,  dis-tik'-e-ah). 
(Gr.  di  =  double  +  stichos  =  row.)  That  condi- 
tion of  the  eyelashes  in  which  a  second  row 
rubs  against  the  cornea,  causing  inflammation. 

Divergence  (di-ver'-gens).  (L.  di  =  apart -f  ver- 
gere  =  to  incline.)  To  turn  outward  from 
parallelism. 

Dividend  (div'-i-dend).  (L.  dividere  =  to  divide.) 
A  number  or  quantity  to  be  divided  by  another 
is  called  the  dividend. 

Donders  (Frans  Cornelis).  A  Dutch  physician, 
born  at  Tilburg,  Holland,  May  27,  1818.  He  was 
educated  at  Utrecht,  where  he  became  a  pro- 
fessor   of    physiology. 

Double  Prism.  An  opaque  disc  found  in  test-case 
with  a  slit-like  opening.  Over  this  slit  there 
are  two  prisms  with  their  bases  together.  Used 
for  testing  for  muscular  imbalance.  To  test  for 
muscular   imbalance   use  a   small  round   bright 


78  LEWIS  POCKET 

frosted  light  (about  %  to  i/4  inch,  at  20  feet), 
the  double  prism  will  make  this  light  appear  as 
two,  both  of  which  will  be  displaced  from  their 
true  position.  Over  the  other  eye  place  the  red 
glass  disc  which  will  color  the  light  red.  The 
patient  will  then  see  three  lights,  two  white, 
one  red.  If  the  red  light  is  seen  midway  be- 
tween the  two  white,  no  muscular  imbalance  is 
present;  if  not,  the  prism  that  will  bring  it 
there  is  the  measure  of  deviation.  The  two 
prisms  used  in  this  disc  are  of  five  diopters 
each,  joined  base  to  base.  When  the  line  formed 
by  the  bases  is  placed  horizontally  before  the 
pupil  of  an  eye  the  light  will  be  seen  as  two, 
separated  vertically  from  their  true  position 
leaving  the  other  eye,  which  is  wearing  the  red 
glass  disc,  to  see  the  light  in  its  true  position. 

Double  Vision.  Seeing  one  object  as  two.  See 
Diplopia. 

Doublet  (doub'-let).    Composed  of  two  lenses. 

Duct  (dukt).   A  tube  for  conveying  a  fluid. 

Dura  Mater.  The  outermost  membrane  of  the 
brain,  spinal  cord,  optic  nerve,  and  capsule  of 
Tenon. 

Dural  Sheath.  The  external  covering  of  the  optic 
nerve. 

Dynameter  (dy-nam'-e-ter).  An  instrument  for  de- 
termining the  magnifying  power  of  telescopes. 

Dynamic  (Gr.  dynamis  =  power).  The  powers 
whereby  bodies  are  put  in  motion. 

Dynamic  Refraction  (dy-nam'-ic).  (Gr.  dynamis  = 
power.)  The  refraction  of  the  eye  (dioptric 
power)  while  using  all  of  its  accommodation 
and  adjusted  for  the  near  point  of  vision.    The 


OPHTHALMIC  DICTIONARY  79 

difference  between  the  dynamic  and  static  re- 
fraction is  known  as  the  Amplitude  of  Accom- 
modation. 

Dynamic  Skiametry  fdi-nam'-lc  sky-am'-e-try). 
(Gr.  dynamis  =  power  -f  skia  =  shadow  -)-  met- 
ron  =  measure.)  Is  defined  as  the  measuring  of 
the  refraction  of  an  eye  by  the  shadow  test 
(retinoscopy)  while  the  accommodation  is  under 
tension.  It  is  the  opposite  of  static  skiametry, 
where  the  accommodation  is  relaxed. 

The  value  of  dynamic  skiametry  is  said  to  be 
in  its  offering  a  mechanical  means  for  absorb- 
ing spasms  of  accommodation,  and  thus  reveal- 
ing latent  errors  v/ithout  recourse  to  cyclopleg- 
ics.  In  the  practice  of  the  dynamic  method  the 
patient  is  required  to  accurately  fix  his  vision 
on  a  test  card  that  is  situated  the  same  distance 
away  (say,  16  inches)  that  the  nodal  point  of 
an  examiner's  eye  (behind  the  peephole  of  his 
skiascope)  is  situated  during  the  examination; 
that  is,  the  fixation  and  observation  must  be 
exactly  the  same.  Under  these  conditions,  if 
the  examiner  will  keep  adding  all  the  plus 
spherical  lens  power  possible  before  reversal  of 
the  shadow  takes  place  (even  though  the 
shadow  does  not  indicate  hyperopia)  it  will  be 
found  that  an  eye  will  surrender  that  portion 
of  its  accommodation  which  is  in  excess  of  what 
is  needed  to  correctly  harmonize  with  the  con- 
vergence required  for  the  distance  at  which  the 
examination  is  made.  With  the  dynamic  method 
no  allowance  in  strength  of  lens  is  made  for  the 
working  distance,  as  by  the  static  method,  and 
where  the  patient  is  presbyopic  or  has  latent 


hyperopia  there  will  be  a  difference  in  the  find- 
ings between  the  dynamic  and  static. 

The  recognized  text-book  on  the  subject  is 
called  "Dynamic  Skiametry  in  Theory  and  Prac- 
tice," by  Andrew  Jay  Cross,  D.O.S.,  of  Columbia 
University,  New  York  City,  who  is  the  origi- 
nator of  the  method. 
Dynamometer  (dy-na-mom'-e-ter).  An  instrument 
for  measuring  force  or  power;  especially  the 
muscular  power. 

Dynamometry  (dy'-na-mom'-e-try).   The  process  of 

measuring  force  while  doing  work. 
Dyslexia    (dis-lex'-se-ah).     (Gr.    dys  =  bad  +  lexis 

=  word.)    Inability  to  read  caused  by  a  disease 

of  the  brain.    Vision  is  good,  but  the  power  to 

read  is  wanting. 

Dysopsy  (dys-op'-sy).    (Gr.  dys  =  faulty -f- opsis  = 
vision.)     Dimness  of  vision. 


Hi  CCENTRIC  (ek-sen'-trik).  (Gr.  ek  =  out  + 
kentron  =  center.)     Away  from  a  center. 

Ecchymosis  (Gr.  ek  =  out  -f  chymos  =  juice).  An 
extravasation  of  blood  into  tissue. 

Ectasia  (ek-ta'-se-ah).  Abnormal  distention  or 
dilatation  of  a  part. 

Ectiris  Cek-ti'-ris).  (Gr.  ektos  =  outside  +  iris.) 
The  external  portion  of  the  iris. 

Ectochoroidea  (ek-to-cho-roi'-de-ah).  (Gr.  ektos  = 
outside.)    The  outer  layer  of  the  choroid  coat. 

Ectocornea  (ek-to-kor'-ne-ah).  Outer  layer  of  the 
cornea. 


OPHTHALMIC  DICTIO^sARY  81 

Ectoretina  (ek-to-ret'-in-ah).  (Gr.  ektos  =  out- 
side.)   Outermost  layer  of  the  retina. 

Ectropion  (ek-tro'-pi-on)  Ectropium  (Gr.  ek  =  out 
+  trope  =^  a  turning).  Turning  out  or  inside 
out  of  the  edge  of  an  eyelid. 

Edema  (e-de'-mah).  (Gr.  oidema  =  a  swelling.) 
An  accumulation  of  serum  in  the  cellular  tissue. 

Efferent  (ef'-er-ent).  (L.  effere  =  to  bring  out.) 
Conveying  outward,  as  from  center  to  periph- 
ery; applied  to  motor  nerves  and  vessels  con- 
veying from  the  center.    The  opposite  of  afferent. 

Embolism  (Gr.  embolisma  =  a  patch).  Obstruc- 
tion of  a  vessel  by  an  embolus. 

Em 'bolus.  A  clot  or  plug  which  obstructs  a  blood- 
vessel. 

Emergent  ("to  come  out  of").  A  ray  of  light  after 
having  passed  through  a  refracting  medium. 

Emissive.    Radiating. 

Emmetropia  (em-met-ro'-pi-ah).  (Gr.  emmetros  = 
in    measure  -^  ops  =  eye.)      That    condition    in 


An  emmetropic  eye  receiving  one  set  of  parallel  rays. 
It  must  be  remembered  that  the  three  rays  representing 
the  set  come  from  one  point,  but  the  point  is  so  far  away 
that  the  rays  appear  to  be  parallel  because  the  divergence 
is  so  slight. 

which  all  parallel  rays  of  light  after  entering 
the  eye  are  brought  to  a  focus  on  its   retina, 


ijrL<>>io    IT  Kjy^r\.i:^  ± 


while  th^  muscles  of  accommodation  are  in  a 
state  of  rest. 

Emmetropia  has  no  reference  whatever  to 
sight,  or  disease,  but  simply  means  that  the 
optical  apparatus  has  the  correct  focal  length 
for  the  globe  of  the  eye.  In  other  words,  no  lens 
is  required  for  distant  vision.  When  this  condi- 
tion does  not  exist  the  eye  is  out  of  measure,  or 
ametropic. 

Emphyse'ma  (Gr.  en  =  in  +  physema  =  a  blow- 
ing). The  infiltration  of  air  into  the  cellular 
tissues  of  the  orbit.  May  be  caused  by  rupture 
of  the  lachrymal  sac. 

Encan'this  (Gr.  en  =  in  +  kanthos  =  canthus).  A 
minute  tumor  in  the  inner  canthus  of  the  eye. 

Endothelium  (Gr.  endon  =  within  +  thele  =  nip- 
ple). A  layer  of  flat  cells  lining  serous  cavities, 
blood-vessels,  and  lymphatics.  The  fifth  layer 
of  the  cornea. 

Energy.    (Physics)  Capacity  for  performing  work. 

Enervate  (en-er-vate).  To  deprive  of  nerve,  force, 
or  strength;    to  render  feeble. 

Enophthalmus  (en-of-thal'-mus).  (Gr.  en  =  in -f 
ophthalmos  =  eye.)  A  condition  where  the  eyes 
are  deep-seated. 

Enstrophe  (en*-stro-fe).  (Gr.  en  =  in  -f  strophe  = 
a  turning).  A  turning  inward. 

En'tad  (Gr.  entos  =  within).   Toward  a  center. 

Entochoroidea  (en-to-cho-roi'-de-ah).  (Gr.  entos  = 
within  4-  chorioeides  =  choroid).  The  inner  layer 
of  the  choroid. 

Entocornea  (en-to-cor'-ne-ah).  (Gr.  entos  =  with- 
in.)   Descemet's  membrane. 


OPHTHALMIC  DICTIONARY  83 

Entoptic  (en-top'-tic).  (Gr.  entos  =  within -f  op- 
tikos  ^  visual.)    Situated  within  the  eye. 

Entoptic  Phenomenon  (en-top'-tic  phe-nom'-e-non). 
That  which  is  peculiar  with  itself,  such  as 
Muscae  Volitantes. 

Entoptoscopy  (en-top-tos'-co-py).  (Gr.  entos  = 
within  +  optos  ==  visible  +  skopeo  =  I  view.) 
Inspection  of  the  interior  of  the  eye. 

Entoretina  (en-to-ret'-in-ah).  The  nervous  or  inner 
layer  of  the  retina. 

Entropion  (Gr.  en  =  im  +  trope  =  a  turning).  See 
Entropium. 

Entropium  ( en-tro'-pi-um).  A  turning  in  or  inver- 
sion of  the  eyelid  or  eyelashes. 

Enucleate  (e-nu'-cle-ate).  (L.  e  =  from -f- nucleus 
=  kernel.)    To  remove  from  its  cover. 

Enucleation  fe-nu'-cle-a'-shun).  Operation  for  the 
removal  of  the  eye. 

Ephidro'sis.  (Gr.  "I  sweat.")  An  excessive  se- 
cretion of  the  sweat  glands  of  the  eyelids.  It 
causes  itching,  irritation,  and  inflammation  of 
the  skin  and  conjunctiva.    It  is  difficult  to  cure. 

Epicanthus  (ep-i-can'-thus).  (Gr.  epi  =  upon -|- 
kanthos  =  canthus.)  A  fold  of  skin  projected 
over  the  inner  canthus. 

Epiphora  (e-pif'-or-a).  (Gr.  epi  =  upon  +  phoria 
=  tending.)  An  overflow  of  tears,  causing  them 
to  run  down  the  cheek. 

Episclera  (Gr.  epi  ^  upon  +  skleros  =  hard).  The 
connective  tissue  between  the  sclera  and  the 
conjunctiva. 

Episcleral  (ep-i-scle'-ral).  Situated  over  the  sclera 
of  the  eye. 


S4  LEWIS  POCKET 

Episcleritis  (ep-i-scle-ri'-tis).  Inflammation  of  the 
outer  layers  of  the  sclera. 

Epithello'ma.  Cancer  composed  largely  of  epithe- 
lial cells,  and  is  the  most  frequent  of  malignant 
growths  affecting  the  eyelid.  It  seldom  appears 
before  the  age  of  forty. 

Epithelium  (ep-i-the'-le-um).  (Gr.  epi  =  upon + 
thele  =  nipple.)  The  non-vascular,  external 
layer  of  the  skin  and  mucous  membrane.  First 
layer  of  the  cornea. 

Equal  (e'-kwal).  (L.  aequalis  =  equal.)  Having 
the  same  value. 

Equation  (e-kwa'-shun).  A  proposition  asserting 
the  equality  of  two  quantities  and  expressed  by 
the  sign  "  =  "  between  them.  In  Algebra,  an 
equality  which  exists  only  for  particular  values 
of  certain  letters  called  unknown  quantities. 

Equilateral  (e-kwi-lat'-e-ral).  (L.  aequus  =  equal 
-f  latus  =  side.)    Having  all  of  the  sides  equal. 

Equil'ibrating  Operation.  Tenotomy  of  the  muscle, 
which  antagonizes  a  paralyzed  muscle  of  the 
eye. 

Errors  of  Refraction.  Abnormal  conditions  of  re- 
fraction in  the  eye. 

Erythropsia  (erythro'-psia).  (Gr.  erythros  =  red  -f 
opsis  =  vision.)  Red  vision;  a  condition  in 
which  all  objects  appear  to  be  tinged  with  red. 

Eserine  (es'-er-een).  An  alkaloid  obtained  from 
the  calabar-bean,  which  will  cause  contraction 
of  the  pupil.  It  has  an  action  exactly  opposite  to 
that  of  atropine,  since  it  places  the  iris  and 
ciliary  muscle  in  a  state  of  tonic  contraction. 
Consequently,  miosis  develops,  so  that  the  pupil 
is  about  the  size  of  a  pin's  head,  with  adjust- 


OiilTHALMIC  DICTIONARY  85 

merit  of  the  eye  for  the  near  point,  as  if 
marked  myopia  were  present.  We  generally 
apply  sulphate  of  eserine  in  1  per  cent  solution. 
This  solution,  when  freshly  prepared,  is  color- 
less, but  after  some  days  becomes  red,  although 
without  losing  its  activity.  The  instillation  of 
eserine  produces,  simultaneously  with  the 
changes  in  the  iris,  a  feeling  of  great  tension 
in  the  eye,  and  frequently  headache,  and  even 
nausea,  so  that  with  many  persons  it  cannot  be 
employed.  For  this  reason,  hydrochloride  of 
pilocarpine,  prescribed  in  a  1  to  2  per  cent  solu- 
tion, is  recommended  as  a  miotic  for  ordinary 
use.  Its  solution  keeps  better  than  that  of 
eserine,  and  does  not  act  as  powerfully  as  the 
latter,  but  is  not  accompanied  by  any  unpleas- 
ant complication.  Eserine  is  best  reserved  for 
those  cases  in  which  pilocarpine  is  ineffectual. 

Esophoria  (es-o-fo'-ri-ah).  (Gr.  eso  =  inward + 
phoria  =  a  tending.)  That  condition  of  the  eyes 
in  which  the  visual  axes,  although  parallel  when 
in  use  for  distant  vision,  deviate  inward  when 
the  extrinsic  muscles  are  in  a  state  of  rest. 

Esotropia  (e-so-tro'-pi-ah).  (Gr.  eso  =  inward + 
trope  =  turn.)  This  term  expresses  a  stronger 
meaning  than  Esophoria,  in  which  there  is 
merely  a  tendency,  while  in  Esotropia  there  is 
a  positive  and  visible  appearance  of  the  eyes 
turning  inward. 

Evolution  (ev-o-lu'-shun).  (L.  evolvere  ==  to  un- 
roll.)   The  extraction  of  roots  from  powers. 

Excavation  (ex-cav-a'-shun).  (L.  excavare  —  to 
hollow  out.)  Excavation  of  optic  nerve;  cupping 
or  hollowing  of  the  optic  disc. 


86  LEWIS  POCKET 

Exophoria  (ex-o-fo'-ri-ah).  (Gr.  exo  =  outward + 
pliora  ^^  a  tending.)  That  condition  of  the  eyes 
in  which  the  visual  axes,  although  parallel  when 
in  use  for  distant  vision,  deviate  outward  when 
the  extrinsic  muscles  are  in  a  state  of  rest. 
The  internal  rectus  muscles  are  overworked 
from  this  continual  convergence  and  relieved 
only  when  the  lids  are  closed,  or  prisms  worn, 
base  in,  that  are  strong  enough  to  bend  the  light 
to  suit  the  eyes  in  their  deviating  position  of 
rest. 

Excphthalmic  Goiter  (eks-off-thal'-mik  goi'-ter).  A 
goiter  with  exophthalmos  and  cardiac  palpita- 
tion; Basedow's  disease;  Graves'  disease.  The 
most  prominent  symptoms  are  protrusion  of  the 
eye,  excited  action  of  the  heart,  enlarged  thy- 
roid (goiter),  and  certain  nervous  phenomena. 
The  protrusion  is  almost  invariably  bilateral, 
though  not  infrequently  greater  on  the  right 
side.  The  upper  lids  do  not  follow  the  eyeball 
in  looking  down  (Von  Graefe's  sign) ;  infre- 
quency  of  involuntary  winking  (Stellwag's  sign) 
and  abnormal  width  of  the  palpebral  aperture 
are  also  found. 

Exophthalmos  (ex-of-thal'-mos).  (Gr.  ex  =  out  + 
ophthalmos  =  eye.)  Abnormal  protrusion  of  the 
eye. 

Exor'bitism  (Jj.  ex  =  out  +  orbita  =^  orbit).  Pro- 
trusion of  the  eyeball. 

Exotropia  (ex-o-tro'-pi-ah).  (Gr.  exo  =  outward  + 
trope  =  turn.)  When  the  eye  is  turned  outward 
from  parallelism.     See  Divergent  Strabismus. 

Extraction     (ex-trak'-shun).      (L.     extrahere  =  tu 


OPHTHALMIC  DICTIONARY 


87 


draw  out.)    The  removal  of  a  body  by  surgical 
means. 

Extravasation  (eks-trah-vas-a'-shun).  (L.  extra  = 
out  of  -f  vas  =  vessel.)  The  escape  of  fluids 
from  their  proper  vessels,  into  surrounding- 
tissues. 

Extremes  (eks-tremz').  (L.  extremus  =  outer- 
most.) The  first  and  last  terms  of  a  proportion 
or  of  any  other  related  series  of  terms. 

Extrin'sic.  Of  exterior  origin.  E.  Muscles  are 
those  on  the  outside  of  the  organ. 

Eye  (L.  oculus  =  eye).  The  organ  of  sight.  The 
function  of  each  eye,  taken  singly,  is  to  form 
upon  the  retina,  or  nervous   membrane  which 


Eye. 


lines  the  inside  and  back  part  of  the  organ,  a 
sharply  defined  inverted  image  of  any  object 
looked  at.  The  eye  resembles  a  photographer's 
camera  inasmuch  as  the  image  produced  upon 
the  retina  is  precisely  the  same  as  that  pro- 
duced on  the  ground  glass  of  a  camera.  By 
means  of  the  optic  nerve  the  image  that  is  re- 
ceived on  the  retina  is  conveyed  to  the  brain, 
which  recognizes  the  visual  appearances  and 
completes  the  act  of  seeing.  More  than  this  we 
do  not  know,  but  we  do  know  that  it  depends 
upon  the  sharpness  and  clearness  of  the  retinal 
image.  If  the  image  is  blurred  and  indistinct  it 
will  be  impossible  for  the  brain  to  recognize  the 
object  accurately. 

Eyebrows.  They  are  two  projecting  arches  of  in- 
tegument covered  with  short,  thick  hairs,  which 
form  the  upper  boundaries  of  the  orbits. 

Eye  Ground.  The  inside  and  back  part  of  the  eye. 
The  Fundus. 

Eyelashes.   The  hair  of  the  eyelids. 

Eyelids.  The  anterior  covering  of  the  eye;  that 
portion  of  movable  skin  with  which  the  eyeball 
is  cpvered  or  uncovered  at  will,  protecting  it 
from  injury  by  their  closure.  The  upper  lid  is 
the  larger,  the  more  movable  of  the  two,  and  is 
supplied  by  a  separate  muscle,  levator  palpeb- 
rae  superioris.  When  the  eyelids  are  open  an 
elliptical  space  is  left  between  their  margins,' 
the  extremities  of  which  correspond  to  the 
junction  of  the  upper  and  lower  lids,  and  are 
called  canthi.  The  outer  canthus  is  more  acute 
than  the  inner,  and  the  lids  here  lie  in  close 
contact  with  the  globe,  but  the  inner  canthus  is 
prolonged  for  a  short  distance  inward,  toward 


OPHTHALMIC  DICTIONARY 


89 


the  nose,  and  the  two  lids  are  separated  by  a 
triangular  space,  the  lacus  lachrymalis.  At  the 
commencement  of  the  lacus  lachrymalis  and  on 
the  margin  of  each  eyelid  is  a  small  conical 
elevation,  the  lachrymal  papilla  (the  puncta), 
the  apex  of  which  is  pierced  by  a  small  orifice, 
the  commencement  of  the  lachrymal  canal. 
Structures  of  the  Eyelids:  The  eyelids  are  com- 
posed of  the  following  structures,  taken  in  their 
order  from  without  inward:  Integument,  areolar 
tissue,  fibers  of  the  orbicularis  muscle,  tarsal 
cartilage,  fibrous  membrane,  meibomian  glands, 
and  conjunctiva.  The  upper  lid  has,  in  addition, 
the  aponeurosis  of  the  levator  palpebrae.  The 
integument   is   extremely  thin,   and   continuous 


POSTERIOR   VIEW   OF   EYELID   SHOWING   HOW   THE 
TEARS    ENTER   THE   CONJUNCTIVA. 

1.      Orbioularis   Palpebrarum    Muscle. 

'2.      Opening   between    the    lids    (Palpebral    Fissure.) 

3.  Lachrymal     Glands,     where     the     tears     have     their 
orfgin. 

4.  Its  ducts  opening  in  the  fold   of  the  Conjunctiva. 
r>.      Conjunctiva    lining    inside    of    lid. 

G.      Puncta    I^acrimalia,    through    which    the    tears    pass. 
7.      Inner   Canthus. 


at  the  innrfriii  of  tin-  lids  wiih  »h«'  coiijuncl  v  .1. 
The  Subcutaneous  Areolar  Tissue  in  vrry  \h\ 
and  delicate,  seldom  contains  any  fal,  and  is 
extr«  I     '     '     *  '     t(t  srrouB  infiltration. 


PO8TEIIIOU     VIKW     .'!•     TH  \1,     <I£YKL1I>) 

WITH     THK    <«».\Jl  .M    ii\  A     ui   MuVKD. 

1.  Orl»Jn    of    \hr    Triinor-tariil    Mii»<  Ir. 

2,  Hupcrlor    (U>li(jut<    Mu*i  !•■    ■■»•••     VNiolnir    •»' •> 

Trochlea. 

8.  Inferior    Oblhiur    Mu«rl< 

4  Atlachtnonl  of  <^rblrulnrlH  r.iIi>oliri«run»  "H  >  .••.! 
•iflp. 

rv.  Tariial  Carill»c<ii  vhowing  position  of  MvlboiiflMtt 
Olnndii 

n  Opening  l>«iwv«n  ih»  lids  known  mm  xh*  Palp^lM .  '. 
FlNCurp 

7.      i^wer    part    of   Orblrularln    Palpebrarum    Mop<I<. 

H  The  Inarrilon  of  the  Trnaor-taral  Jkluiirlr  nrar  i».' 
Puncta. 

9.  I^rhrymal  Sac  In  th«  no**. 

Eyepiece.  Th«'  lens  or  combination  of  lenses  m( 
thr  !•>»•  «'n(l  of  a  tfloHcopi-  or  othrr  optical  In- 
Hlrtiment.  through  whirh  th«'  imaRe  form«»d  by 
the  object  glass  is  viewed. 

Eyesight.  Tho  sense  of  seeing:  sl^tht  of  the  oyo; 
vifwinu;   obHorvation. 


OPHTHALMIC  DICTIONARY  91 

Jr  ACTOR  (fak'-tor).  (L.  facere -- to  do.)  One  of 
two  or  more  numbers  which  when  multiplied 
together   produce   a   given   number. 

Facultative  (fak'-ul-ta-tiv).  (L.  facultas  =  faculty.) 
The  power  or  ability  to  maintain  extra  effort 
whenever  called  upon. 

Falling  Eyelashes.     (See  Milphae  and  Madarosis.) 
False  Image.    The  image  seen  wath  the  deviating 
eye. 

False  Myopia.  Due  to  a  spasm  of  accommoda- 
tion, where  the  crystalline  lens  is  kept  con- 
vexed  by  the  spasm  and  simulates  true  myopia. 

Far  Point.  The  far  point  or  punctum  remotum  is 
the  most  distant  point  at  which  an  object  may 
be  seen  clearly,  with  the  muscles  of  accommo- 
dation at  rest.  Properly  speaking,  the  far  point 
is  an  optical  and  not  a  visual  point,  and  is  that 
point  from  which  rays  of  light  will  focus  on 
the  retina,  the  eye  being  in  a  state  of  rest. 

Fascia  (fash'-e-ah).  A  band  or  sheet  of  tissue 
connecting  and  investing  muscles. 

Field   of   Vision.     The   area   or   space   which  the 

fixed  eye  can  see. 

Filtration  Angle.     (See  Iritic  Angle.) 

Fissure  (fish'-ur).  (L.  findo  =  to  split.)  In  anat- 
omy, a  cleft,  or  slit.  Palpebral  fissure  is  the 
opening  between  the  margins  of  the  eyelids. 
Sphenoidal  fissure  is  a  large  split-like  opening 
situated  in  the  upper  and  back  part  of  the  orbit. 
Spheno-maxillary  fissure  is  an  opening  in  the 
back  part  of  the  orbit  between  the  sphenoid, 
maxillary  and   palate   and   malar   bones.     Cho- 


92  LEWIS  POCKET 

roidal  fissure  is  the  opening  in  the  choroid 
through  which  the  optic  nerve  passes  to  form 
the  retina. 

Flap  Extraction.  Removal  of  cataract  by  making 
a  flap  in  the  cornea. 

Floating  Specks.  Small  floating  opacities  in  the 
humors  of  the  eye.     (See  Muscae  Volitantes.) 

Focal  (fo'-kal).  Pertaining  to  a  focus.  F.  Depth, 
penetrating  power  of  a  lens.  F.  Distance,  dis- 
tance between  the  center  of  lens  and  its  prin- 
cipal focus. 

Focal  Length  of  Lenses,  in  inches,  centimeters 
and  millimeters  taken  from  the  basis  of  forty 
inches  as  the  equivalent  to  one  meter. 

English 
Dioptrics  Inches  Centimeters  Millimeters 

.12 333   833 8333 

25 160   400   4000 

.37 108   270   2703 

.50 80   200   2000 

.62 641/:, 161   1613 


.75 53   133  1333 

.87 46   115  1150 

1.00 40   100  1000 

1.12 36   89  893 

1.25 32   80  800 

1.37 .'  29  73  730 

1.50 27   67  667 

1.62 25 62  617 

1.75 23   .57  571 

1.87 21   54  535 

2.00 20   50  500 

2.25 18   44  444 

2.50 16   40  400 

2.75 15   36  364 


OPHTHALMIC  DICTIONARY  93 

■^  English 

Dioptries  Inches  Centimeters  Millimeters 

3.00 13  33  333 

3.25 12   31   308 

3.50 11   29  286 

3.75 lOVo 27   267 

4.00 10  25   250 

4.50 9   22   222 

5.00 8   20   200 

5.50 7   18   182 

6.00 6il> 17  167 

6.50 6   15  154 

7.00 51/2 14   143 

7.50 514 13   133 

8.00 5   12  VL' 125 

9.00 41/2 11   Ill 

10.00 4   10   100 

11.00 3Vi: 9   91 

12.00 314 8   83 

13.00 3   71/2 77 

14.00 274 7 71 

15.00 2% 6% 662{j 

16.00 21/0 61/4 621;^ 

18.00 214 5Vj 551/2 

20.00 2 5 50 

The  above  table  is  approximately  correct,  yet 
there  is  a  slight  difference  in  close  figuring,  but 
is  correct  as  far  as  the  optometrist  is  con- 
cerned; for  instance,  a  +  1-D.  lens  has  a  focal 
length  of  39.37  inches,  while  we  call  it  40. 
Focal  Planes.  Straight  lines  through  the  foci  per- 
pendicular to  the  principal  axis. 
Focus  (fo'-kus).  The  point  produced  by  light 
coming  to  or  going  from  a  point.  First  Princi- 
pal Focus  Is  at  the  point  the  light  leaves  as 
divergent   rays   and   emerges   from   the   optical 


94  LEWIS  POCKET 

system  as  parallel  to  the  principal  axis.  The 
Second  Principal  Focus  is  the  point  where  the 
emergent  rays  cross  each  other  when  the  inci- 
dent rays  have  been  parallel  to  the  principal 
axis.  Negative  Focus  is  the  point  from  which 
rays  of  light  appear,  to,  but  do  not  come  from, 
the  focus  of  a  minus  lens.  Secondary  Focus. 
Any  focus  of  the  secondary  axis. 

Fogging  System.  The  system  of  fitting  glasses  by 
first  making  the  patient  artificially  myopic  by 
means  of  plus  spheres,  if  they  are  not  already 
myopic,  the  idea  being  to  relax  all  accommoda- 
tion before  using  cylinders. 

Folders.  A  term  employed  for  eye-glasses  that 
can  be  folded  up  and  placed  in  a  small  pocket. 

Follicle  (fol'-ik-l).  (L.  folliculus  =  a  small  bag.) 
•A  small  secretory  cavity  or  sac. 

Follicular  (fol-ik'-u-lar).  Containing  follicles.  F. 
Conjunctivitis.  A  form  of  conjunctivitis  marked 
by  the  presence  of  follicles.  This  occurs  gen- 
erally in  children,  and  is  characterized  by  the 
formation  of  small,  clear  elevations,  consisting 
of  adenoid  tissue,  in  the  conjunctiva  of  the 
lower  lid;  in  some  cases  they  are  present  also 
in  tl  e  retrotarsal  fold  of  the  upper  lid. 

Fontana,  Spaces  of.  In  the  anterior  chamber  of 
the  eye,  where  the  corneal  margin  joins  the 
base  of  iris  and  sclerotic,  we  find  a  number  of 
delicate  bands  of  tissue  passing  from  the  mem- 
brane of  Descemet  to  the  base  of  the  iris.  These 
are  known  as  the  ligamentum  pectinatum  iridis 
and  between  them  small  comb-like  openings 
leading   into    Schlemm's   Canal,    known   as    the 


o< 


OPHTHALMIC  DICTIONARY  95 

Foramen  (fo-ray'-men).  (L.  foro  ==  to  bore  a  hole.) 
A  hole  or  opening  through  any  bone  or  a  mem- 
branous structure.  Infraorbital  F.,  the  external 
opening  of  the  infraorbital  canal,  on  the  an- 
terior surface  of  the  body  of  the  maxilla;  optic 
F.,  the  opening  between  the  lesser  wing  and 
body  of  the  sphenoid  transmitting  the  optic 
nerve  and  ophthalmic  artery.  (For  other  fora- 
men, see  under  orbit.) 

Force.  (L.  fortis  =  strong.)  (Physics.)  Any 
action  between  two  bodies  which  changes,  or 
tends  to  change,  their  relative  condition  as  to 
rest  or  motion;  or,  more  generally,  which 
changes  or,  tends  to  change,  any  physical  rela- 
tion between  them,  whether  mechanical,  chem- 
ical, or  any  other  kind;  as,  the  force  of  gravity. 

Fornix.     (L.  arch,  vault.)     A  vault-like  space. 

Fornix  Conjunctiva.  The  turn  or  fold  of  the  con- 
junctiva. 

Fossae  Patellaris  (pa-tel-la'-ris)  (meaning  dish- 
like depression).  The  depression  in  the  anterior 
surface  of  the  vitreous  body  in  which  the  crys- 
talline lens  lies.    Also  called  the  Hyaloid  Fossa, 

Tossa.     (L.  a  ditch.)     A  pit,  cavity  or  depression. 

Fovea  (foh'-ve-ah).  (L.  fodio  =  to  dig.)  A  small 
depression.  F.  Centralis  is  employed  to  desig- 
nate the  little  depression  m  the  center  of  the 
macula  lutea. 

I  Fraction   (frak'-shun).     (L.  f rangere  =  to  break.) 
One  or  more  of  the  equal  parts  of  a  unit. 

Frame  Fitting.  There  are  times  when  patients 
complain  that  their  glasses  are  not  comfortable, 
yet  they  have  the  right  correction.     The  cause 


96 


LEWIS   POCKET 


of  the  trouble  is  sometimes  found  in  the  im- 
proper adjustment  of  the  frames.  The  fitting  of 
a  frame  is  very  important,  and  if  neglected  will 
sometimes  destroy  the  benefit  of  the  most  care- 
fully fitted  lenses.  When  a  student  understands 
the  relation  between  accommodation  and  con- 
vergence the  value  of  frame  fitting  becomes 
easily  understood.  A  convex  lens,  with  its 
curved  surfaces,  may  be  described  as  made  up 
of  an  infinite  number  of  prisms  with  their 
bases  meeting  at  the  center:  a  concave  lens,  in 
a  like  manner,  is  made  up  of  an  infinite  number 


Frame  Fitting. 

of  prisms  with  their  bases  outward.  When  a, 
person  looks  through  the  inner  side  of  a  convex 
lens,  as  he  is  compelled  to  do  when  the  frames 
are  too  wide  for  the  pupillary  distance,  he  is 
looking  not  only  through  convex  lenses,  but 
also  through  prisms  with  their  bases  outward: 
when  the  frames  are  too  narrow  he  looks 
through  prisms  with  their  bases  inward.  With 
concave  lenses,  of  course,  this  condition  will 
be    reversed,    and    besides    giving    a    prismatic 


effect,  will  cause  the  unbalancing  of  accommo- 
dation and  convergence. 

The  subject  of  frame  fitting  has  always  been 
and  always  will  be  more  or  less  of  a  problem  to 
the  student,  but  after  a  little  practice  and  care- 
ful attention  it  becomes  a  very  easy  matter.  I 
will  here  mention  a  few  points  which  may  be  of 
assistance  to  my  fellow-student: 

1st.  See  that  the  pupillary  distance  is  cor- 
rect and  that  the  patient  is  looking  through  the 
center  of  lenses.  If  glasses  are  to  be  worn 
constantly  it  is  best  for  the  adjuster  to  stand 
off,  say,  about  three  feet,  and  direct  the  pa- 
tient to  look  between  his  eyes,  so  adjusting 
frames  that  the  patient  will  be  looking  through 
the  centers  of  lenses.  For  reading  glasses  the 
optical  centers  should  be  slightly  closer  and 
lower,  and  the  top  of  the  lenses  must  be  in- 
clined forward,  so  as  to  be  as  near  as  possible 
at  right  angles  to  the  line  of  vision.  In  this 
way  better  vision  is   enjoyed. 

2d.  The  lenses  should  be  placed  as  near  the 
eye  as  the  lashes  will  permit. 

3d.  Never  prescribe  a  small  lens  for  a  large 
fiace  nor  a  large  lens  for  a  small  face,  but 
always  make  the  lenses  as  large  as  you  possibly 
can  without  interfering  with  the  patient's  ap- 
pearance, and  at  the  same  time  see  that  the 
pupillary  distance  is  correct.  In  the  fitting  of 
spectacles  see  that  the  angle  of  crest  saddles 
the  nose  nicely,  and  that  the  temples  are  long 
enough  to  go  around  the  ear  without  showing 
underneath.  See  that  the  temples  are  not  too 
far  from  the  face  and  at  the  same  rime  do  not 


08  LEWIS   POCKET 

press  on  the  flesh.  If  you  desire  to  tilt  the 
lenses  do  not  bend  temples,  but  bend  the  end 
piece.  All  glasses  should  tilt  outward  from  the 
top,  but  reading  glasses  more  than  distant  ones. 
Cylinders  should  always  be  worn  as  spectacles, 
as  it  is  very  important  that  they  should  be  held 
in  their  correct  position. 

It  is  always  best  for  one  who  is  just  com- 
mencing to  practice  to  supply  himself  with  a 
full  set  of  measuring  frames.  They  are  put  up 
and  sold  by  all  wholesale  optical  houses.  The 
optical  houses  also  supply  cards  on  which  are 
printed  the  various  dimensions.  Then  by  find- 
ing a  sample  frame  among  your  set  that  about 
fits  your  patient  you  lay  it  down  on  the  card, 
allowing  for  any  change  you  wish  to  make,  and 
you  can  easily  figure  the  exact  dimensions. 

Function  (funk'-shun).  (L.  functio  =  to  execute.) 
The  special  duties  which  an  organ  or  group  of 
organs  has  to  perform.  (Math.)  A  quantity  so 
connected  with  another  quantity  that  if  any 
alteration  be  made  in  the  latter  there  will  be  a 
consequent  alteration  in  the  former.  Each 
quantity  is  said  to  be  a  function  of  the  other. 
Thus,  the  circumference  of  a  circle  is  a  function 
of  the  diameter. 

Fundus  (fun'-dus).  That  portion  of  a  hollow  organ 
farthest  from  the  entrance.  The  fundus  of  the 
eye  is  seen  by  means  of  the  ophthalmoscope, 
namely,  the  retina,  blood  vessels,  choroid,  optic 
disc,  collectively. 

Fuscin  (fus'-sin).  (L.  fuscus  =  dusky.)  A  brown 
pigment  of  the  retinal  epithelium. 


OPHTHALMIC  DICTIONARY  99 

WANGLION  (gang'-gle-on).  (Gr.  "a  knot.")  In 
anatomy,  a  knot-like  aggregation  of  nerve  cells. 
It  Is  a  partly  independent  nerve  center,  with  dis- 
tinct functions  in  connection  with  nearby  struc- 
tures. Ciliary  G.,  sometimes  called  ophthalmic 
or  lenticular,  is  about  the  size  of  a  pin's  head, 
situated  in  the  back  part  of  the  orbit,  between 
the  external  rectus  muscle  and  the  optic  nerve. 
The  three  nerves  which  enter  it  are,  one  from 
the  nasal  branch  of  the  ophthalmic  (sensory), 
one  from  a  branch  of  the  third  nerve  (motor), 
and  a  root  of  the  sympathetic.  From  it  passes 
off  about  ten  filaments  which  pierce  the  poste- 
rior part  of  the  sclera  supplying  the  ciliary 
muscles,  the  iris,  and  the  cornea.  Gasserian  or 
Semilunar  G.  lies  in  a  depression  (cavum 
Meckelii)  oh  the  anterior  surface  of  the  petrous 
portion  of  the  temporal  bone  near  the  apex.  It 
is  a  flat  expansion  on  the  sensory  root  of  the 
(fifth)  trigeminal  nerve,  receiving  on  its  inner 
side  filaments  from  the  carotid  plexus  of  the 
sympathetic  and  giving  off  the  ophthalmic, 
superior  maxillary  and  inferior  maxillary.  The 
ophthalmic  nerve  is  a  sensor  nerve.  It  supplies 
sensation  to  cornea,  ciliary  muscles,  iris,  lach- 
rimal  gland,  mucous  membrane  of  nose,  skin  of 
eyelids,  eyebrows,  forehead  and  nose.  Just  be- 
fore entering  the  orbit,  through  the  sphenoidal 
fissure,  it  divides  into  three  branches,  lachrimal, 
frontal  and  nasal. 

Geomeirical  Center.  A  point  midway  between  aJl 
edges.  • 

Geometry.      (Gr.   geometria  =  to  measure.)     That 


100  LE^^'IS  I»OCKET 

branch  of  mathematics  which  investigates  the 
relations,  properties  and  measurement  of  solids,, 
surfaces,  lines  and  angles;    the  science  which 
treats  of  the  properties  and  relations  of  magni- 
tudes; the  science  and  relations  of  space. 

Generic  Compounds.  Lenses  having  spherical 
and  cylindrical  curvatures  of  the  same  species; 
that  is,  both  convex  or  both  concave.  Con- 
trageneric  compounds  have  one  surface  convex, 
the  other  concave. 

Glabei'la,  Glaberium.  (L.  glaber  =  smooth.)  Space 
between  the  eyebrows. 

Gland.  (L.  glans  =  acorn.)  The  name  applied  to 
organs  which  separate  from  the  blood  any  fluid 
whatever. 

Bruch's  Glands.  The  lymph-follicles  of  the 
conjunctiva.  Henle's  Glands  are  a  number  of 
follicular  cavities  formed  by  irregular  folds 
in    the    epithelium    of    the    tarsal    conjunctiva. 

Krause's  Glands,  the  tubular  glands  which  lie 
at  the  border  of  the  tarsi  near  the  fornix.  These 
are  regarded  as  accessory  glands.  Ciliary 
Glands  are  the  sweat  glands  of  the  eyelids  and 
located  in  several  rows  close  to  the  free  margin 
of  the  lid.  They  are  also  known  as  the  Glands 
of  Moll.  Lachrimal  Glands,  the  glands  which 
secrete  the  tears.  They  are  located  in  a  depres- 
sion of  the  frontal  bone  at  the  upper  and  outer 
angle  of  the  orbits.  The  gland  is  divided  into 
two  parts,  the  superior  and  inferior  and  at- 
tached to  the  bony  roof  of  the  orbit  by  the 
tarso-orbital  fascia.  The  ducts,  about  ten  in 
number,  open  into  the  fornix  conjunctiva.  Its 
nerve    supply    is    the    smallest    of    the    three 


OPHTHALMIC  DICTIONARY  rOl 

branches  of  the  ophthalmic  and  known  as  the 
lachrimal  nerve.  Meibomian  Glands  (see  Mei- 
bomian).   Tarsal  Glands  (same  as  Meibomian). 

Glass.  A  hard,  brittle,  artificial  substance  formed 
by  the  fusion  of  silica,  potash  and  lead.  Under 
the  best  conditions  it  is  quite  transparent. 
Nothing  definitely  is  known  as  to  its  origin. 
The  Egyptians  used  it,  and  glass  has  been  dis- 
covered amongst  the  ruins  of  Pompeii. 

The  media  out  of  which  lenses  are  made. 
Crown  glass  for  optical  lenses,  sometimes  com- 
bined with  flint  glass. 

Glaucoma  (glau-ko'-mah).  (Gr.  glaukos  =  green- 
ish gray.)  A  disease  of  the  eye  characterized 
by  increased  intraocular  tension.  In  order  to 
fully  understand  this  disease  it  will  be  neces- 
sary to  study  thoroughly  the  anatomy  of  the 
eye,  and  in  doing  so  pay  particular  attention 
to  Schlemm's  Canal  and  the  Spaces  of  Fontana, 
situated  in  the  first  tunic  between  the  sclerotic 
and  cornea.  These  canals  are  said  to  carry 
away  the  excess  of  aqueous  humor.  The  theory 
most  generally  accepted  is,  that  the  vitreous 
humor  is  formed  in  the  choroid  and  ciliary  body 
and  passes  through  the  hyaloid  membrane  into 
the  vitreous  cavity;  from  there  it  filters  through 
the  suspensory  ligaments  into  the  posterior 
chamber,  where  it  becomes  watery,  and  is 
known  as  the  aqueous  humor.  After  passing 
through  the  pupil  into  the  anterior  chamber  it 
is  said  to  pass  through  the  Spaces  of  Fontana 
into  Schlemm's  Canal.  In  this  way  one  can 
readily  see  that  if  the  iris  was  attached  to  the 
lens,  as  it  is  in  cases  of  iritis,  or  by  the  strain- 
ing of  the  ciliary  muscles,  as  m  hypermetropia, 


102  LEWIS  POCKET 

thus  closing  the  Spaces  of  Fontana,  the  drain- 
age system  would  be  blocked,  while  the  humors 
continue  forming,  resulting  in  .a  painful  intra- 
ocular pressure.  Glaucoma  may  be  divided  into 
two  kinds,  primary  and  secondary.  Primary, 
when  it  makes  its  appearance  in  a  healthy  eye, 
or  with  a  disease  like  cataract.  Secondary, 
Avhen  caused  by  a  disease  like  iritis.  It  is  a 
progressive  disease,  and  unless  checked  by 
treatment  ends  in  permanent  blindness. 

Symptoms  of  Glaucoma.  (1)  Pain,  sometimes 
of  a  neuralgic  character.  (2)  Increased  tension 
of  the  eyeball,  sometimes  becoming  stonelike. 
(3)  Rapid  failing  of  the  power  of  accommoda- 
tion. (4)  Dimness  of  vision.  The  pupil  is 
dilated  and  sluggish.  (.5)  The  patient  complains 
of  seeing  flashes  of  light  and  colored  halo 
around  a  flame  or  candle.  (6)  Cupping  of  the 
optic  disc.  (7)  Conjunctivitis.  The  iris  also 
appears  steamy.  When  glaucoma  is  suspected 
the  patient  should  be  sent  to  an  oculist  at  once. 

The  use  of  atropine  causes  the  iris  to  crowd 
into  the  periphery  of  the  anterior  chamber, 
somewhat  occluding  the  Spaces  of  Fontana  and 
interfering  with  the  free  exit  of  aqueous  humor. 
As  the  intraocular  tension  increases,  the  stop- 
page becomes  more  complete.  When  the  atro- 
pine is  discontinued  the  sphincter  muscle  of  the 
pupil  draws  the  iris  away  from  the  Spaces  of 
Fontana  and  the  normal  outlet  is  again  opened. 
As  age  advances,  the  sphincter  loses  its  power, 
and  frequently  in  old  people  fails  to  pull  the  iris 
away  from  the  Spaces  of  Fontana,  and  this  con- 
dition may  result  in  glaucoma.    For  the  reasons 


OPHTHALMIC  DICTIONARY  103 

mentioned  it  is,  as  a  rule,  unsafe  to  use  atro- 
pine after  the  ages  of  from  30  to  35. 

Glaucomatous    (glau-korn'-at-ous.)      Of  the  nature 

of  glaucoma. 
Glioma    (gly-oh'-mah).      (Gr.    glia  =  glue  +  oma.) 

A  malignant  tumor  of  the  retina. 

Gllosarco'ma.     Glioma  combined  with  sarcoma. 
Globulin  (glob'-u-lin).     (L.  globulus  =  globule.)    A 
proteid  from  the  lens. 

Goggles.  Spectacles  with  wire  screens  for  the 
eyes. 

Goiter  (goi'-ter).  (L.  guttur  =  throat.)  An  en- 
largement of  the  thyroid  gland.  Exophthalmic  g. 
(See  Exophthalmic  Goiter.) 

Gonorrhe'al  Ophthalmia.  (Gr.  gonos  =  semen -h 
rhoia  =  a  flow.  Ophthalmus  =  eye.)  The  most 
acute  form  of  purulent  conjunctivitis.  It  is 
caused  by  the  Introduction  of  the  urethral  dis- 
charge to  the  conjunctival  sac. 

Graduated  Tenotomy.  (L.  gradus  =  a  degree.  Gr. 
tenon  =  tendon  -f  tome  =  incision.)  An  incom- 
plete cutting  of  the  tendon  of  an  eye  muscle. 

Granular  Lids  (Trachoma).  (L.  granulum,  dim  of 
granum  ^=  grain.)  Roughness  and  soreness  of 
the  inside  of  the  eyelids.  This  roughness  is 
caused  by  a  swelling  of  the  lymph-corpuscles, 
forming,  as  it  were,  little  lymphatic  glands  or 
lymphatic  follicles. 

Gran'ule.     A  small  rounded  body.     G.  Layer,  one 

of  the  layers  of  the  retina. 

Gravity  (grav'-i-ty).  (L.  gravitas  =  heavy.)  The 
state  of  having  weight.  (Physics.)  The  ten- 
dency of  a  mass  of  matter  toward  a  center  of 


104  LEWIS  POCKET 

attraction.  Specific  gravity,  the  ratio  of  the 
weight  of  a  body  to  the  weight  of  an  equal 
volume  of  some  other  body  taken  as  the  stand- 
ard or  unit.  This  standard  is  usually  water  for 
solids  and  liquids,  and  air  for  gases.  Thus,  19, 
the  specific  gravity  of  gold,  expresses  the  fact 
that,  bulk  for  bulk,  gold  is  19  times  as  heavy  as 
water. 

Gravitation  (grav-i-ta'-shun).  The  act  of  gravi- 
tating. (Physics.)  That  kind  of  attraction  or 
force  by  which  all  bodies  in  the  universe  tend 
toward  each  other. 

Groove  (groov).  A  furrow,  crease  or  sulcus.  A 
narrow,  elongated  depression  on  any  surface. 
Lachrimal  G.,  the  bony  channel  which  lodges 
the  lacrimal  sac.  It  is  located  at  the  anterior 
and  inner  part  of  the  orbit;  cavernous  G.,  car- 
otid sulcus,  the  groove  on  the  upper  surface  or 
the  sphenoid  bone,  supporting  the  cavernous 
sinus  and  the  carotid  artery;  optic  G.,  a  groove 
on  the  upper  surface  of  the  sphenoid  bone  be- 
tween the  optic  foramen  in  which  rest  the  optic 
commissure. 


H 


ALLER'S    CIRCLES.       Arterial    and    venous 

circles  within  the  eye. 
Halo.     (Gr.  halos  =  a  circular  threshing  floor.)   A 

reddish  yellow  ring  surrounding  the  optic  disc. 
Ha'lo  Glaumato'sus.     A  whitish  ring  around  the 

optic  disc  in  glaucoma. 
Ha'lo  Symptom.     Seeing  of  colored  rings  around 

lights.   This  is  a  symptom  of  incipient  glaucoma. 
Hec'tometer.    One  hundred  meters. 


OPHTHALMIC    DICTIOXAUV  105 

Helcol'ogy.  (Gr.  helkos  =  ulcer  +  logia  =  study.) 
Science  of  ulcers. 

Helco'sis.  (Gr.  helkos  —  ulcer  and  suffix  osis  = 
condition.)     The  formation  of  an  ulcer. 

Hemeralopia  (hem-er-a-lo'-pi-ah).  (Gr.  hemera -- 
day  -f  alaos  =^  obscure  +  ops  eye.)  Day  blind- 
ness, better  vision  in  a  dim  light. 

Hemiachromatopsia  (hem-i-a-chro-mat-op'-si-ah ) . 
(Gr.  hemi  —  half  -f-  a  ^  without  +  chroma  ^^ 
color  +  opsis  —  vision.)  Color  blindness  in  one- 
half,  or  in  corresponding  halves,  of  visual  field. 

Hemianopia  (hem-i-an-o'-pi-ah).  Hemianopsia.  (Gr. 
hemi  ^-  half  +  an  without  +  opsis  —  vision. ) 
Blindness  for  one-half  the  field  of  vision  in  one 
or  both  eyes. 

Hemiopic  (hem-e-op'-lk)  ("half  vision").  That 
condition  of  the  eye  in  which  only  half  of  the 
object  is  seen. 

Hemophthal'mla,  Hemophthal'mus.  (Gr.  haima  =- 
blood  -f  ophthalmos  =  eye.)  Extravasation  of 
the  blood  inside  of  the  eye. 

Hemorrhage  fhem'-or-aj).  (Gr.  haima -^  blood + 
rhagia  to  burst.)  Escape  of  blood  from  the 
veins  or  arteries. 

Hering's  Theory.  This  is  a  doctrine  which  holds 
that  color-perceptions  are  dependent  on  a  visual 
substance  in  the  retina,  which  is  variously  mod- 
ified by  anabolism  for  black,  green,  or  blue,  and 
by  catabolism  for  white,  red  and  yellow. 

Heterochromia   (het-ero-kro'-me-ah).    (Gr.  heteros 
other -f  chroma       color.)       A     difference     iu 
color   (in  the  irides  or  of  different  parts  of  the 
same  iris  J. 


106  LEWIS  POCKET 

Heterometropia  (het-er-o-me-tro'-pi-ah).  (Gv.  het- 
eros  =  other  +  metron  =  measure  -f  ops  = 
eye.)  That  condition  in  which  the  refractive 
power  is  unlike  in  the  two  eyes. 

Heteronymous  (het-er-on'-im-us).  (Gr.  heteron- 
ymos  =  having  a  different  name.)  Crossed. 
See  Diplopia. 

Heterophoral'gia.    Pain  with  heterophoria. 

Heterophoria  (het-er-o-pho'-ri-a).  (Gr.  heteros  = 
other  +  phoria  =  tending.)  That  condition  of 
the  eyes  in  which  the  visual  axes,  although 
parallel  when  in  use  for  distant  vision,  deviate 
in  another  direction  when  the  extrinsic  muscles 
are  in  a  state  of  rest.  It  is  subdivided  into 
eight  kinds.  When  the  eyes  have  a  tendency 
to  turn  in  it  is  known  as  esophoria;  if  a  ten- 
dency to  turn  out,  it  is  known  as  exophoria;  if 
a  tendency  to  turn  up,  it  is  known  as  hyper- 
phoria; if  up  and  in,  hyperesophoria,  and  if  up 
and  out,  hyperexophoria;  if  a  tendency  down- 
ward, it  is  known  as  cataphoria;  and  if  down 
and  in,  esocataphoria;  if  down  and  out,  exocata- 
phoria.  Any  error  of  refraction  is  liable  to 
bring  on  Heterophoria,  and  by  correcting  the 
error,  the  Heterophoria  may  disappear,  though 
it  may  linger  for  a  month  or  two.  Again  one 
muscle  may  be  too  short  or  too  long  and  a 
prism  will  have  to  be  worn,  thus  allowing  the 
eyes  to  deviate  in  order  to  avoid  strain. 

Heterophthal'mos.  (Gr.  heteros  =  other  +  oph- 
thalmos  =  eye.)  That  condition  in  which  the 
irides  differ  in  color. 

Heterotropia  (het-er-o-tro'-pi-a).  (Gr.  heteros  = 
other  +  trope  =  I  turn.)     A  condition  in  which 


OPHTHALMIC  DICTIONARY  107 

the  extrinsic  muscles  are  no  longer  able  to  hold 
the  eyes  parallel  and  there  is  a  positive  and 
visible  appearance  of  their  deviating.  They 
may  turn  in  any  direction,  as  in  heterophoria; 
if  upward,  hypertropia;  if  downward,  hypotro- 
pia  or  catatropia;  if  inward,  esotropia;  if  out- 
ward, exotropia.  For  permanent  deviation,  see 
Strabismus. 

Hippus  (hip'-us).  (Gr.  hippos  =  horse  so  named 
from  its  irregular  movement.)  Spasmodic 
pupillary  movements,  independent  of  the  action 
of  light. 

Histology  (his-toF-o-je).  (Gr.  histos  =  tissue + 
logia  =  discourse.)  The  science  of  the  minute 
structure  and  composition  of  tissues. 

Holmgren's  Test  (holm'-grens).  A  color  test  with 
a  number  of  different  colored  yarns  represent- 
ing the  various  shades  of  different  colors.  Used 
for  detecting  color  blindness. 

Homocentric  Rays  (ho-mo-sen'-tric).  (Gr.  homos  = 
same  -[-  kentron  =  center.)  A  conic  pencil  of 
light  rays. 

Homonymous.  (Gr.  homonymos  =  of  the  same 
name.)     See  Diplopia. 

Hordeolum  (hawr-dee'-o-lum).  (L.  hordeum  = 
barley.)  Sty;  inflammation  of  sebaceous  glands 
of  the  eyelid. 

Horizon  (ho-ri'-zun).  (L.  horizon  =  the  boundary 
line.)  The  circle  which  bounds  that  part  of 
the  earth's  surface  visible  to  a  spectator  from 
a  given  point;  the  apparent  junction  of  the 
earth  and  sky. 

Horizontal  Line  (hor-i-zon'-tal.)  A  constructive 
line,   either  drawn  or   imagined,   which   passes 


108  LEWIS  POCKET 

through  the  point  of  sight,  and  is  the  chief  line 
in  the  projection  upon  which  all  verticals  are 
fixed,  and  upon  which  all  vanishing  points  are 
found.  Horizontal  plane  is  a  plane  parallel  to 
the  horizon,  upon  which  it  is  assumed  that  ob- 
jects are  projected. 

Horny   Epithelium.     Trachomatous  conjunctivitis. 

Horopter  (ho-rop'-tur).  (Gr.  horos  =  limit + 
opter  =  one  who  sees.)  The  field  of  binocular 
vision  as  seen  with  the  eyes  fixed. 

Hot  Eye.  Temporary  congestion  of  the  eye.  This 
is  seen  in  gouty  patients. 

Humor.  (L.  humere  =  to  be  moist.)  A  fluid  ele- 
ment of  the  eye.  (Aqueous,  crystalline  lens  and 
vitreous.) 

Hutchinson's  Pupil.  One  that  is  dilated  on  one 
side. 

Hiyaline  (hi'-al-in).     (Gr.  hyalos  =  glass.)     Glassy. 

Hyalitis  (hy-al-i'-tis).  Inflammation  of  the  vitre- 
ous humor  or  hyaloid  membrane. 

Hyaloid  (hy'-al-oid).  (Gr.  hyalos  =  glass  -f  eidos  = 
resemblance.)  That  which  resembles  glass  in 
its  transparent  qualities.  Hyaloid  membrane 
surrounds  and  encloses  the  vitreous  humor  and 
forms  the  suspensory  ligaments. 

Hyaloid  Artery.     The  fetal  branch  of  the  central 

artery  of  the  retina. 
Hyaloid   Canal,   or   Canal   of   Stilling.     The   canal 

through    the    vitreous    body,    occupied    by    the 

hyaloid  artery  during  fetal  life. 

Hyaloid  Fossa.  (Gr.  hyalos  =  glass  +  L.  fossa  = 
ditch.)     The  depression  in  the  anterior  surface 


OPHTHALMIC  DICTIONARY  100 

of  the  hyaloid  membrane  in  which  the  crystal- 
line lens  lies. 

Hyaloid  Membrane.  The  delicate  transparent 
membrane  which  forms  a  sac  and  contains  the 
vitreous  humor,  and  forms  the  suspensory  liga- 
ments of  the  lens  and  the  Zone  of  Zinn. 

Hydrophthalmia  (hy-drof-thal'-mi-ah),  Hydroph- 
thalmus.  (Gr.  hydro  =  water  +  ophthalmos  = 
eye.)     Increase  in  the  fluid  contents  of  the  eye. 

Hydrops  (hi'-drops)  (dropsy).  An  abnormal  col- 
lection of  fluid  in  any  part  of  the  body. 

Hygroma  (hi-gro'-mah).  (Gr.  hygros  =  fluid -1- 
oma  =  tumor.)     A  sac  or  cyst  filled  with  fluid. 

Hyperaesthesia  (hi-per-as-the'-si-ah).  (Gr.  hyper  = 
overmuch  +  aisthesis  =  sensation.)  Over-sensi- 
tiveness. H.  of  Retina,  over-sensitiveness  of 
the  retina. 

Hyperchromatism  (hy'-per-chro'-ma-tism).  (Gr.  hy- 
per =  overmuch  +  chroma  =  color.)  Having  an 
unusual  intensity  of  color. 

Hyperemia  (hi-per-e'-me-ah).  (Gr.  hyper  =over -f- 
haima  =  blood.)  A  condition  where  there  is  an 
abnormal  fullness  of  the  blood  vessels.  H.  of 
the  eyelids  is  often  a  forerunner  of  inflamma- 
tion. It  is  usually  accompanied  by  a  slight 
marginal  blepharitis  and  even  conjunctivitis, 
and  if  these  are  relieved  the  hyperemia  to  a 
great  extent  will  disappear. 

Hyperkeratosis  (hy-per-ker-at-o'-sis).  Hypertrophy 
of  the  cornea. 

Hypermetropia  (hy-per-me-tro'-pi-ah).  (Gr.  hy- 
per =  over  +  metron  =  measure  -f  ops  =  eye.) 
(Far  sighted.)     An  error  of  refraction,   where 


'ilO  LEWIS  POCKET 

parallel  rays  of  light  focus  back  of  the  retina 
with  the  muscles  of  accommodation  at  rest,  due 
to  the  shortness  of  the  eye  from  before,  back 
or  insufficient  curvature  of  the  dioptric  media. 
Subdivided  into  three  classes — latent,  manifest 
and  total.  Latent  h.  has  no  subdivisions;  it  is 
hypermetropia  that  is  hidden  by  cramp  of  the 
ciliary  muscle,  and  will  not  relax  without  the 
use  of  drugs  at  the  time  of  fitting,  but  when 
the  correction  for  the  manifest  is  worn,  the 
cramp  begins  to  relax  and  more  hypermetropia 
becomes  manifest.  It  may  take  a  week  or  a 
year.  Manifest  h.  is  that  part  found  and  cor- 
rected with  the  trial  case  and  retinoscope.  It 
is  said  to  have  three  subdivisions,  namely, 
facultative,  relative  and  absolute.  Facultative  h. 
is  where  the  patient  has  the  ability  to  overcome 


A  hypermetropic  eye.  The  heavy  lines  show  the  focus 
of  parallel  rays  behind  the  retina.  The  dotted  lines 
«how    the    effect    of   accommodation    upon    the   same    rays. 

his  error  by  accommodation,  and  sees  well  at 
all  distances.  Glasses  relieve  strain,  but  do  not 
improve  vision  in  this  case.  Relative  h.  is  where 
it  is  possible  to  accommodate  for  a  near  point, 
by  converging  to  a  point  still  nearer — in  fact, 
by  squinting.  This  eye  has  blurred  vision  for 
close  work,   and   plus   spheres   improve   vision. 


OPHTHALMIC  DICTIONARY  111 

Absolute  h.  is  where  the  error  exceeds  the 
amount  of  the  accommodation,  and  the  patient 
is  unable  to  bring  the  focus  to  the  retina,  and 
vision  is  blurred  at  all  distances.  The  correc- 
tion always  improves  vision.  Total  h.  is  the  full 
amount  of  hypermetropia  the  patient  has.  For 
instance,  we  correct  the  eye  with  the  trial  case 
and  find  2-D.  of  manifest;  then  by  the  use  of 
drugs  relax  any  cramp;  and  now  find  that  the 
same  eye  has  6-D.  of  hypermetropia.  4-D.  was 
hidden  by  cramp.  This  we  call  latent,  6-D., 
being  the  total  amount  of  hypermetropia. 

Hyperope  (hi'-per-op).  A  person  who  has  hyper- 
metropia. 

Hyperopia  (hi-per-o'-pe-ah);  (Gr.  hyper  =  over  + 
ops  =  eye.)      See   Hypermetropia. 

Hyperphoria  (hyper- fo'-ri-ah).  (Gr.  hyper  = 
above -f  phoria  =  tending.)  That  condition  in 
which  one  of  the  eyes,  although  parallel  with 
its  fellow  when  in  use  for  distant  vision,  devi- 
ates upward  when  the  extrinsic  muscles  are  in 
a  state  of  rest. 

Hyperplasia  (hi-per-pla'-ze-ah).  (Gr.  hyper  = 
above  +  plasis  =  a  moulding).  Excessive  tissue 
formation. 

Hypertrophy  (hy-per'-tro-fy),  (Gr.  hyper  =  above 
+  trophe  =  nourishment.)  An  abnormal  in- 
crease in  the  size  of  a  part  or  an  organ. 

Hypertropia  (hy-per-tro'-pi-ah).  (Gr.  hyper  = 
above  +  trope  =  turn.)  Elevation  of  one  visual 
axis  above  the  other. 

Hyphemia  (hi-fe'-me-ah).  (Gr.  hypo  =  below -f- 
haima  =  blood.)     Hemorrhage  within  the  eye. 


112  LEWIS  POCKET 

Hypnogenet'ic.  (Gr.  hypnos  =  sleep  +  genesis  = 
production.)     Causing  or  producing  sleep. 

Hypnolepsy  (hip'-no-lep-se).  (Gr.  hypnos  ^=  sleep 
+  lepsis  =  a  seizing.)     Abnormal  sleepiness. 

Hypometropia  (hy-po-me-tro'-pi-ali).  (Gr.  hypo  = 
under  4-  metron  =  measure  +  ops  =  eye.)  See 
Myopia  and  Brachymetropia. 

Hypophoria  (hi-po-fo'-re-ah).  (Gr.  hypo  =  below  + 
phoria  =  tending.)  That  condition  in  which  one 
of  the  eyes,  although  parallel  with  its  fellow 
when  in  use  for  distant  vision,  deviates  down- 
ward when  the  extrinsic  muscles  are  in  a  state 
of  rest. 

Hypopyon  (hi-po'-pe-on).  (Gr.  hypo  =  beneath -|- 
pyon  =  pus.)  Pus  in  the  anterior  chamber  of 
the  eye. 

Hypotenuse  (hi-pot'-e-nus).  (Gr.  hypo  =  under + 
teinein  =  to  stretch.)  The  side  of  a  right- 
angled  triangle  opposite  the  right  angle. 

Hypotonia  (hi-po-to'-ne-ah).  (Gr.  hypo  =  under  + 
tonos  =  tone.)    Diminished  intraocular  tension. 

Hypotonus  (hi-pot'-o-nus).     See  Hypotonia. 

Hypotony  (hi-pot'-o-ne).     See  Hypotonia. 


I 


DENTICAL  POINTS.  When  the  image  falls  on 
corresponding  points  on  the  retinae  of  the  two 
eyes. 

IHaqueation  (il-lak-we-a'-shun).  (L.  illaqueare  = 
to  ensnare.)  The  curing  of  ingrowing  eye- 
lashes by  drawing  with  a  loop. 

Illumination  (il-lu-min-a'-shun).  (L.  illuminare  = 
to  light  up.)     The  lighting  up  of  a  place  or  ot- 


ject  for  inspection.  Focal  i.,  when  light  is 
brought  to  a  focal  point  by  lens  or  mirror. 
Axial  i.,  when  light  is  transmitted  or  reflected 
along  the  axis  of  a  lens.  Direct  i.,  light  thrown 
directly  upon  the  object.  Oblique  i.,  when  an 
object  is  illuminated  from  one  side. 

Illusion  (il-lu'-shun).  (L.  illudere  =  to  mock.)  An 
unreal  image  presented  to  the  mental  vision. 

Image  (im'-ej).  (L.  imago  =  likeness.)  A  picture 
or  conception  of  anything  real.  Aerial  i.,  image 
seen  as  in  the  air  by  the  ophthalmoscope.  Di- 
rect i.,  Erect  i.,  and  Virtual  i.,  formed  by  rays 
not  yet  focused.  An  upright  image.  False  !., 
image  formed  on  the  retina  of  the  deviating  eye 
in  strabismus.  Optical  I.,  an  appearance  of  an 
object  created  by  refraction  or  reflection. 

Imbalance.  That  condition  in  which  the  eyes 
tend  to  deviate  from  parallelism  with  the  ex- 
trinsic muscles  in  a  state  of  rest.  See  hetero- 
phoria 

Inadequacy.  (L.  in  =  not  +  adaequare  =  to  be 
equal.)      Unable  to  perform  allotted  function. 

Incident.  (L.  incidere  =^  to  fall  into  or  upon.) 
Falling  or  striking  upon,  as  a  ray  of  light  upon 
a  reflection  surface. 

In'cident  Ray.  The  name  given  to  a  ray  of  light 
before  it  strikes  the  second  medium. 

Index  of  Refraction.  The  refracting  or  bending 
power  of  the  medium  as  compared  with  air,  the 
normal  standard,  and  the  index  of  which  is  the 
unit  1.  Water  as  compared  with  air  is  1.33; 
crown  glass,  1.52;  flint  glass.  1.62  +  ;  pebble. 
1.54;  diamond,  2.4,  the  greatest  index  of  any 
known  medium.     The  transparent  parts  of  the 


114  LEWIS  POCKET 

eye  in  their  order  are  as  follows;  the  cornea, 
1.33;  the  aqueous  humor,  1.33;  the  crystalline 
lens,  1.43,  and  vitreous  humor,  1.33.  Different 
indices  of  refraction  would  mean  different  den- 
sities. 

Induction  (in-duk'-shun).  (Physics.)  The  prop- 
erty by  which  one  body,  having  electrical  or 
magnetic  force,  induces  it  in  another  body  with- 
out direct  contact. 

Inertia  (in-er'-shi-a).  (L.  idleness.)  (Physics.) 
That  property  of  matter  by  which  it  tends  when 
at  rest  to  remain  so,  and  when  in  motion  to 
continue  in  motion,  and  in  the  same  straight 
line  or  direction  unless  acted  upon  by  some 
external  force. 

Infiltration  (in-fil-tra'-shun).  (L.  in,  and  filtrare  = 
to  filter.)  The  act  or  process  of  infiltrating  a 
fluid  into  the  cellular  tissue. 

Infinite  Distance.  When  rays  of  light  proceed 
from  a  distance  of  twenty  feet  or  more  they  are 
considered  parallel,  and  are  said  to  come  from 
infinity. 

Inflammation  (in-flam-ma'-shun).  (L.  inflammare  = 
to  burn.)  A  diseased  condition  characterized  by 
redness,  pain,  heat  and  swelling.  Traumatic  i., 
that  which  follows  a  wound  or  injury. 

Inflection  (in-flek'-shun).  (L.  in  =  in  +  flectere  = 
to  bend.)  The  act  of  bending  inward  or  that 
state  of  being  bent  inward. 

Infra.  A  prefix  denoting  a  position  below  the 
part  denoted  by  the  word  to  which  it  is  joined. 

Infraductlon,  Deorsumvergence.  The  act  or  power 
of  turning  one  eye  downward  from  its  fellow. 


^ 


OPHTHALMIC  DICTIONARY  115 

Infraorbital  (in-fra-or'-bi-tal).  Situated  beneath 
the  orbit. 

Innervation  (in-nerv-a'-shun).  (L.  in  =  not + 
nervus  =  nerve.)  The  sending  of  nervous  stimu- 
lus or  power  to  an  organ  through  its  nerves. 

Innervate  (in-nerv'-et).  To  supply  with  nerves; 
to  give  nervous  stimulus  to. 


INSTRUMENTS    AND   THEIR    USES 

Amblyoscope.  An  instrument  to  stimulate, 
exercise  and  develop  the  fusion  faculty  in  stra- 
bismus, or  squinting  patients. 

Color  Test  (Holmgren's).  A  set  of  worsteds, 
consisting  of  various  shades  and  tints,  for  test- 
ing color  blindness. 

Focimeter  (fo-sim'-e-ter).  An  instrument  for 
measuring  the  focal  lengths  of  lenses  or  com- 
bination of  lenses. 

Keratometer.     See  Ophthalmometer. 

Kryptoscope.  An  instrument  used  for  testing 
strain  in  ophthalmic  lenses.  With  this  instru- 
ment strain  can  be  detected  in  fused  (kryptok) 
lenses  or  when  the  screw  holding  a  lens  in  its 
frame  is  too  tight. 

Latest  Optometer.  An  instrument  combining 
the   advantages   of   a   fixed   and    revolving   cell 


116  LEWIS  POCKET 

trial  frame,  Stevens  Phorometer,  Rotary  Prism 
and  Maddox  Multiple  Rod. 

Myometer  (my'-o-meter).  An  instrument  for 
diagnosing  and  correcting  muscular  insufficiency 
at  the  near  point  of  vision. 

Ophthalmoscope.  An  instrument  with  which 
the  interior  of  the  eye  may  be  examined.  Also 
the  dioptric  and  pathological  states  may  be  de- 
termined. There  are  many  different  kinds  of 
ophthalmoscopes;  for  instance,  the  Loring  is 
a  small  hand  affair,  which  contains  a  mirror 
and  a  number  of  lenses;  the  self-luminous,  by 
DeZeng,  also  a  hand  instrument;  and  the  com- 
bined ophthalmoscope  and  retinoscope,  a  com- 
bined instrument  for  indirect  ophthalmoscopy 
and  for  retinoscopy.  This  is  a  large  machine 
which  stands  on  a  table. 

Ophthalmometer  or  Keratometer.  An  instru- 
ment for  determining  the  amount  and  axis  of 
corneal  astigmatism,  an  objective  test. 

Ophthalmometroscope.  An  ophthalmoscope 
with  an  attachment  for  measuring  the  refrac- 
tion of  the  eye. 

Perimeter.  An  instrument  for  measuring  the 
visual  field. 

Punctumeter.  A  simple  instrument  for  deter- 
mining the  far  point  and  the  near  point,  there- 
fore the  amount  of  hypermetropia,  myopia,  or 
presbyopia.  It  also  indicates  the  age  of  the 
patient. 

Savage  Monocular  Phorometer  and  Cycio 
Phorometer.  Two  instruments  which  together 
make  a  complete  appliance  for  measuring  all  of 
the  muscles  of  the  eye. 

Skiascope.    A  frame  with  a  serie«?  of  plus  and 


OPHTHA L:\IIC  dictionary  1J7 

minus  spherical  lenses,  to  be  used  in  place  of 
test  frame  and  lenses  when  refracting  a  patient 
by  retinoscopy. 

Stevens     Phorometer.       An     instrument     for 
measuring  muscular  imbalance. 

Stigmatometer.  An  instrument  for  testing  re- 
fraction of  the  eye  by  the  objective  method. 
Also  a  complete  ophthalmoscope  for  the  direct 
examination. 
Insufficiency.  Incapacity  of  normal  action  within 
the  eye. 

integer  (in'-te-ger).     (L.  a  whole  number.) 

Intercilium  (in-ter-sir-e-um).  (L.  inter  =  be- 
tween +  cilium  =  eyelid.)  The  space  between 
the  eyebrows. 

Interorbital  (in-ter-or'-bi-tal).  Situated  between 
the  orbits. 

Inter'nus.  Internal.  The  internal  rectus  muscles 
of  the  eye. 

Interval.  (L.  inter  =  between  +  vallum  =  wall.) 
Sturm's,  or  Focal  i.  In  astigmatism,  is  the  dis- 
tance between  the  two  foci,  at  which  the  prin- 
cipal meridians  meet. 

Intraocular  (in-trah-oc'-u-lar).  Situated  within  the 
globe  of  the  eye. 

Intraocular  Tension.  Pressure  from  the  fluids 
within  the  eye. 

Intraorbital  (in-trah-or'-bit-al).  Situated  within 
the  orbit. 

Involution  (in-vo-lu'-shun),  (L.  involvere  =  to  roll 
up.)  Multiplication  of  a  quantity  into  itself  any 
number  of  times. 

Ir'idal.     Pertaining  lo  the  iris. 


118  LEWIS  POCKET 

Iridectome  (ir-id-ek'-tom).  An  instrument  used 
in  cutting  the  iris  in  iridectomy, 

Iridectomize  (ir-id-ek'-tom-ize).  To  cut  away  a 
part  of  the  iris. 

Iridectomy  (ir-id-ek'-to-my).  (Gr.  iris  +  ektome  = 
excision.)  The  operation  for  removing  a  piece 
from  the  iris  for  the  relief  of  tension  of  the 
eyeball  in  the  case  of  glaucoma,  thus  producing 
an  artificial  pupil. 

Iridencleisis  Hr-id-en-cli'-sis).  (Gr.  iris  +  enkleio  == 
to  enclose.)  An  operation  for  displacing  the 
pupil  from  its  natural  position,  brought  about 
by  drawing  the  iris  into  a  wound  made  near  the 
periphery  of  the  cornea,  and  causing  it  to  be- 
come adherent  there. 

Irideremia  (ir-id-er-e'-mi-ah).  TGr.  iris  +  eremia  = 
to  deprive.)  Defect  or  imperfect  condition  of 
the  iris. 

Irides  (ir'-id-ez).    Plural  of  iris, 

Iridesis  (ir-id'-e-sis),  (Gr.  iris  +  desis  =  to  bind.) 
Strangulation  of  a  part  of  the  iris  to  form  an 
artificial  pupil. 

Iridescent  Vision.  (Gr.  iris  ^  rainbow.)  That  con- 
dition in  which  variously  hued  borders  are  seen 
surrounding  artificial  light. 

Iridic  (i-rid'-ik).     Pertaining  to  the  iris. 

Iridoavulsion  (ir'-i-doh-a-vul'-shun).  A  term  ap- 
plied to  the  total  removal  of  the  iris  when  it  ie 
completely  torn  from  its  periphery. 

Iridocele  (i-rid'-o-se'e).  (Gr.  iris  +  kele  =  hernia.) 
Hernial  protrusion  of  a  slip  of  the  iris. 

Iridochoroiditis  (ir-id-o-ko-roid-i'-tis).  Inflamm?> 
tion  of  the  iris  and  choroid. 


OPHTHALMIC  DICTIONARY  110 

Iridocinesis  ( ir-id-o-sin-e'-sis).  The  movement  of 
the  iris  in  contracting  and  expanding. 

Iridocyclitis  (ir-id-o-syc-li'-tis).  (Gr.  iris  +  kyklos 
=  circle  +  itis  =  inflammation.)  Inflammation 
of  the  iris  and  ciliary  body. 

Iridod'esis.  That  condition  in  which  a  loop  of  iris 
is  drawn  out,  and  strangulated  by  a  fine  ligature 
tied  around  it  over  the  incision;  the  little  loop 
soon  drops  off,  and  the  result  is  a  pear-shaped 
pupil,  with  its  broad  end  toward  the  center. 

iridodialysis  (ir-id-o-di-al'-ys-is).  (Gr.  iris  +  dialy- 
sis =  separation.)  Separation  of  the  iris  from 
the  ciliary  body. 

Irldodonesis  (ir-id-o-do-ne'-sis).  (Gr.  iris  -{-  doneo  = 
agitation.)     Trembling  condition  of  the  iris. 

Iridoncus  (ir-id-on'-kus).  (Gr.  iris  +  onkos  = 
swelling.)     A  tumor  or  swelling  of  the  iris. 

Iridoperiphacitis  (ir-id-o-per'-i-fa-si'-tis).  (Gr.  iris 
+  peri  =  around  +  phakos  =  lens.)  Inflamma- 
tion of'the  capsule  of  the  lens  of  the  eye. 

Iridoplania  (ir-id-o-pla'-ni-ah).  (Gr.  wandering.) 
Trembling  of  the  iris;  irldodonesis. 

Iridoplegia  (ir-id-o-ple'-gi-ah).  (Gr.  iris  +  plege  = 
stroke.)  Paralysis  of  the  iris.  Without  defect 
of  accommodation,  it  usually  affects  only  the 
action  to  light,  reflex  iridoplegia,  the  associated- 
action  remaining.  It  occurs  as  a  very  early 
symptom  in  locomotor  ataxia,  sometimes  with- 
out any  other  symptoms  of  that  disease,  and 
should  always  lead  to  full  investigation.  It  is 
probably  due  to  degeneration  in  that  part  of 
the  nucleus  of  the  third  nerve  which  presides 
over  the  reflex  action  of  the  pupil. 


120  l^EW  IS   POCKET 

Iridorrhexis  (ir-id-or-rhex'-is).  (Gr.  iris  +  rhexis  = 
rupture.)  Rupture  of  the  iris.  Tearing  away  of 
the  margin  of  the  iris. 

Iridosclerot'omy.  (Gr.  iris  +  tome  =  incision.) 
Puncture  of  the  sclerotic  and  of  the  edge  of  the 
iris. 

Iridotomy  (ir-id-ot'-o-my).  (Gr.  iris  +  tome  = 
incision.)  The  operation  whereby  an  artificial 
pupil  is  formed  by  the  natural  gaping  of  a  sim- 
ple incision  in  the  iris.  Iridotomy  is  most  use- 
ful when  the  iris  has  become  tightly  drawn 
toward  the  operation  scar  by  iritis  occurring 
after  a  cataract  has  been  removed. 

Iris.  (Gr.  rainbow.)  So  called  from  its  resem- 
bling the  rainbow  in  its  many  colors.  The 
membrane,  stretched  vertically  in  the  anterior 
part  of  the  eye,  in  the  aqueous  humor,  in  which 
it  forms  a  flat  circular  partition  separating  the 
anterior  from  the  posterior  chamber.  It  is  the 
anterior  part  of  the  second  tunic,  and  is  per- 
forated by  a  circular  opening  called  the  pupil, 
which  is  constantly  varying  in  size,  owing  to  the 
contractions  of  its  two  sets  of  muscles.  Its 
posterior  surface  is  covered  with  a  black  coat 
of  pigment  which  continues  backward  over  the 
ciliary  body  and  choroid.  The  greater  circum- 
ference of  the  iris  is  adherent  to  the  ciliary 
body  and  to  the  sclerotic  by  the  ciliary  liga- 
ment. (Ligamentum  Pectinatum  Irides.)  Its 
arteries  are  from  the  long  ciliary  arteries,  which 
form  two  circles,  one  broad  near  its  circumfer- 
ence, the  other  small  and  seated  around  the 
circumference  of  the  pupil.  Its  veins  empty 
into  the  long  ciliary  veins  and  into  the  Vena 
Vortisosea.     The  pupil  is  contracted  by  the  cir- 


OPHTHALMIC  DICTIONARY  121 

cular  or  sphincter  muscle  supplied  by  the  motor 
oculi  (3d)  nerve  and  dilated  by  the  radiating 
muscle  or  dilator,  which  is  chiefly  supplied  by 
the  sympathetic.  The  iris  gives  the  eye  its 
color,  regulates  the  amount  of  light  which 
enters  and  prevents  spherical  aberration  of  the 
crystalline  lens. 

Iris  Shadow.  The  test  for  maturity,  or  ripened 
cataract;  created  by  oblique  illumination. 

Iritic  (i-rit'-ik).   Pertaining  to  the  iris. 

Iritic  Angle.  The  angle  formed  by  the  junction  of 
the  iris  and  cornea. 

Iritis  (i-ri'-tis).  (Gr.  iris  +  itis  =  inflammation.) 
Inflammation  of  the  iris,  which  is  usually  caused 
by  certain  specific  blood  diseases.  It  often 
occurs  in  the  course  of  ulcers  and  of  wounds 
and  other  injuries  of  the  cornea;  also  with 
sclerotitis  and  keratitis. 

Irregular  Astigmatism.     See  Astigmatism. 

Irritant.  (L.  irritare  ^  to  provoke.)  Causing  irri- 
tation. 

Ischemia  (is-ke'-me-ah).  (Gr.  ischo  =  restrain + 
haima  =  blood.)     Bloodlessness. 

Ischemia  Retinae  (is-ke'-me-ah).  Diminution  of 
arteries  in  the  retina. 

I  so.     (Gr.  isos  equal.)     A  prefix  denoting  equality. 

Isocoria   (i-so-co'-ri-ah).     (Gr.  isos  =  equal  +  kore 

=  pupil.)     Where  the  pupils  in  the  two  eyes  are 

equal. 

Isometropia  (i-so-met-ro'-pi-ah).  (Gr.  isos  =  equal 
-f  metron  =  measure*  +  ops  =  eye.)  The  state 
in  which  both  eyes  are  alike  in  their  refraction. 


122  LEWIS  POCKET 

Isosceles  (i-sos'-e-lez).     (Gr.  isos  =  equal  +  skelos 
=  leg.)     Having  two  sides  equal. 

Isotropic  (trop'-ik).     (Gr.  isos  =equal  +  trope  =  a 
turning.)     Equal  in  refractive  power. 


el  ACER'S  TEST  TYPE.  The  standard  type  for 
close  reading,  a  hand  chart. 

Joffroy's  Symptom.  That  condition  which  exists 
when  patient  suddenly  turns  his  eyes  upward 
and  there  is  absence  of  facial  contraction;  seen 
in  exophthalmic  goiter. 


K 


ATAPHORIA  (kat-a-phor'-ia).  (Gr.  kata  = 
down  +  phoria  =  tending.)  That  condition  in 
which  the  eyes  turn  downward  when  the  ex- 
trinsic muscles  are  in  a  state  of  rest.  Stevens 
gives  50°  for  the  maximum  depression  of  nor- 
mal eyes 

Keratalgia  (ker-at-al'-je-ah).  (Gr.  keras  =  horn -+- 
algos  =  pain.)  That  condition  in  which  there  is 
pain  in  the  cornea. 

Keratectasia  (ker-at-ek-ta'-si-ah).  (Gr.  keras  = 
horn  -f  ektasis  =  extrusion.)  That  condition  in 
which  the  cornea  protrudes. 

Keratitis  (ker-at-i'-tis).  (Gr.  keras  =  horn  +  itis 
=  inflammation.)     Inflammation  of  the  cornea. 

Keratocele  (ker-at'-o-cele).  (Gr.  keras  =  horn -!- 
kele  =^  hernia.)  Corneal  protrusion  of  Desce- 
met's  Membrane. 

Keratoconus  (ker-at-o-ko'-nus).    (Gr.  keras  =  horn 


OPHTHALMIC  DICTIONARY  123 

-f-  konos  =  cone.)  That  condition  in  which  there 
is  a  conical  cornea. 

Keratoglobus  (ker-at-o-glo'-bus).  (Gr.  keras  == 
horn  +  L.  globus  =  ball.)  A  globular  protru- 
sion of  the  cornea. 

Keratohelcosis  (ker-at-o-hel-ko'-sis).  (Gr.  keras  = 
horn  +  helkosis  =  ulceration.)  That  condition 
wherein  there  is  ulceration  of  the  cornea. 

Keratoiri'tls.  (Gr.  keras  =  horn  +  itis  =  inflam- 
mation.) That  condition  wherein  the  cornea 
and  iris  are  inflamed. 

Keratoma.  (Gr.  keras  =  horn  -f  oma  =  tumor.) 
A  horn-like  tumor  or  swelling. 

Keratomalacia  (ker-at-o-ma-la'-she-ah).  (Gr.  keras 
=  horn  +  malakia  =  softness.)  Softening  of 
the  cornea. 

Keratome  (ker'-at-om).  A  knife  for  incising  the 
cornea. 

Keratometer  (ker-at-om'-e-ter).  (Gr.  keras  =  horn 
—  metron  =  measure.)  An  instrument  used  for 
measuring  the  cornea.  It  is  commonly  called 
the  ophthalmometer,  of  which  there  are  several 
different  makes. 

Keratometry  (ker-at-om'-e-try) .  Measurement  of 
corneal  curves. 

Keratomycosis  (ker-at-o-my-ko'-sis).  (Gr.  keras  = 
horn  (cornea)  -f  mykes  =  fungus.)  Fungous 
disease  of  the  cornea. 

Keratonyxis  (ker-at-o-nik'-sis).  Gr.  keras  =  horn 
->-  nyxis  =  a  pricking.)     Puncture  of  the  cornea. 

Keratoplasty  (ker'-at-o-plas-ty).  (Gr.  keras  =  horn 
-f  plasso  =  I  form.)  Plastic  surgery  of  the 
cornea. 


1:^4  i^KWiS   Jr'UCKHJT 

Keratoscleritis  (ker-a-to-skle-ri'-tis).  (Gr.  keras  = 
horn  +  sclera  +  itis.)  Inflammation  of  both 
cornea  and  sclera. 

JKeratoscope  (ker'-at-o-scope).  (Gr.  keras  =  horn 
+  skopeo  =  I  examine.)  Instrument  for  exam- 
ining the  cornea. 

Keratoscopy  (ker-at-os'-ko-pe).  Examination  of 
the  cornea  with  a  keratoscope.    Skiascopy, 

Kerectomy  (ke-rek'-to-me).  (Gr.  keras  =  horn -f 
ectome  ^  excision.)  Removal  of  part  of  the 
cornea. 

Kilometer.    One  thousand  meters. 
Kopiopia    or    Copiopia     (ko-pee-oh'-pee-ah).      (Gr. 
kopos  =  fatigue  +  ops  =  eye.)     See  Asthenopia. 

Korectomia     or     Corectomia     (ko-rek-to'-mee-ah). 

(Gr.    kore  =  pupil  +  extome  =  excision.)       The 

operation   for  artificial   pupil   by   removal   of   a 

part  of  the  iris. 
Korectopia    (kor-ek-to'-pe  ah).      (Gr.   kore  =  pupil 

+  ektopos  =  out  of  place.)     Displacement  of  the 

pupil. 

Koroscopy  (ko-ros'-ko-pee).  (Gr.  kore  =  pupil + 
skopeo  =  I  view.)     See  Retinoscopy. 

Kryptok.  (L.  crypta  =  a  vault;  a  hidden  place.) 
The  name  applied  to  a  bifocal  lens  made  by 
fusing  two  pieces  of  glass  of  different  density 
together,  so  as  to  become  one  integral  piece 
with  no  visible  line  of  demarcation. 


Lachrymal     (lak'-rim-al).       (L.    lacrimal  a 
tear.)     Pertaining  to  tears. 

Lachrymal  Apparatus.     Consists  of  the  lachrymal 


OPHTHALMIC  DICTIONARY  125 

gland  which  secretes  the  tears  and  the  cxsecre- 
tory  ducts  which  convey  the  fluid  to  the  surface 
of  the  eye.    This  fluid  after  passing  over  the  eye 


runs   through   the   puncta    into    the   lachrymal 
canal,  then  to  the  lachrymal  sac  and  along  the 
nasal  duct  into  the  cavity  of  the  nose. 
Lachrymation     (lak-rim-a'-shun).      The    secretion 
and  discharge  of  tears. 

Lachrymotomy    (lak-rim-ot'-o-my).     (L.  lacrima 
a  tear  -|-  G.  tome  =^  incision.)     Operation  for  in 
cision  of  lacrimal  duct  or  sac. 

Lacrimal  Gland.     See  Gland. 

Lacrimal,  Lacrymal.     Same  as  Lachrymal. 

Lacu'nar  Orbitae.  The  roof  of  the  orbit  of  the  eye. 

Lacus.  ( L.  "a  lake.")  The  small  circular  portion 
at  the  nasal  side  of  the  opening  between  the 
eyelids. 

La'cus  Lacrima'lis.  (L.  "lake"  +  lacrima  --  a 
tear.)  The  triangular  space  at  the  inner  can- 
thus  between  the  two  eyelids. 

Laevophoria  (le'-vo-phor'-ia).  (L.  laevus  ^  left -^ 
G.  phoria  =^  tending.)     That  condition  in  which 


126  LEWIS  POCKET 

the   eyes   turn    to   the   left   when   the   extrinsic 
muscles  are  in  a  state  of  rest. 

Lagophthalmus  (lag-of-thar-mus).  That  condition 
In  which  it  is  impossible  to  close  the  eyes! 

Lamella  (lam-el'-ah).  (L.  dim.  of  lamina  ^  plate.) 
A  thin  plate  or  scale.     Lamina. 

Lamina  (lam'-in-a).  (L.  "a  plate.")  A  layer  con- 
sisting" of  a  flat,  thin  membrane. 

Lamina  Crlbrosa  (lam'-in-a  crib-ro'-sa).  (L.  "a 
plate"  -f-  cribrum  =  sieve-like.)  The  perforated 
area  in  the  sclerotic  of  the  eye  through  which 
the  optic  nerve  fibers  pass  to  form  the  retina. 

Lamina  Fus'ca.  (L.  "a  plate"  +  fuscus  =  brown.) 
The  outside  layer  of  the  choroid. 

Landolt,  Edmund,  M.  D.  Ophthalmologist,  born  in 
Aaran,  Switzerland,  in  1846;  pursued  his  profes- 
sional studies  in  the  universities  of  Heidelberg. 
Vienna,  Berlin,  Utrecht  and  Zurich,  graduating 
from  the  latter  in  1869;  then  worked  for  more 
than  a  year  as  Horner's  assistant  in  the  Zurich 
clinic  for  eye  diseases;  in  1874  he  established 
himself  in  Paris  as  an  ophthalmologist.  His  in- 
vestigations in  his  specialty  have  been  distin- 
guished by  their  originality.  Among  his  works 
are  "On  the  Retina,"  "A  Manual  of  Ophthal- 
moscopy," published  in  French,  English,  Ger- 
man and  Spanish;  "The  Refraction  and  Accom- 
modation of  the  Eye." 

Lapsus  (lap'-sus).  The  dropping  of  the  upper  lid. 
produced  by  a  paralysis  of  the  levator  palpebra 
muscle.     Synonym,  Ptosis. 

Lashes.  The  name  given  to  the  hairs  of  the  eye- 
lids. 


OPHTHALMIC  DICTIONARY  1:>7 

Latent  (la'-tent).  (L.  latere  =  to  be  concealed.) 
That  which  is  not  apparent  or  manifest.  See 
Hypermetropia. 

Layer.  A  stratum  having  a  certain  amount  of 
thickness  and  serving  the  purpose  of  a  covering. 

Leber's  Disease  (La'-berz).  (Theodor  Leber,  Ger- 
man Ophthalmologist,  1840.)  Atrophy  of  the 
optic  nerve,  which  is  hereditary. 

Lema  (le'-ma).  The  dry,  hard,  yellowish  Incrusta- 
tions which  collect  in  the  inner  canthus. 

Lens.  (L.  "a  lentil.")  The  term  lens  was  first 
applied  to  any  transparent  refracting  body 
which  had  two  spherical  surfaces,  on  account 
of  its  resemblance  to  a  vegetable  known  as  a 
lentil.  A  lens  is  a  transparent  substance,  crown 
or  flint  glass  chiefly,  ground  with  regular  curva- 
ture on  one  or  both  of  its  opposite  sides,  but  not 
parallel  to  each  other,  through  which  an  object 
may  appear  to  be  increased  or  decreased  in  size, 
and  may  have  either  convex  or  concave  spher- 
ical or  cylindrical  surfaces.  There  are  six  vari- 
eties of  spherical  lenses — three  plus  and  three 
minus — all  of  which  can  be  made  the  same  diop- 
tric power,  the  only  difference  being  in  the 
shape  of  the  lens.  Plus  or  positive  lenses  are 
thickest  in  the  center.  Minus  or  negative  lenses 
are  thinnest  at  their  centers.  A  plus  sphere  will 
refract  the  same  in  all  its  meridians  and  con- 
verge parallel  rays  of  light  to  a  point  of  focus, 
while  a  minus  sphere  will  diverge  parallel  rays 
from  a  point.  The  different  forms  of  plus  and 
minus  spherical  lenses  are  here  represented: 

A  line  passing  through  the  optical  center  at 
right  angles  to  the  surfaces  of  these  lenses  is 


128 


LEWIS  POCKET 


not  refracted,  and  is  known  as  the  principal 
axis,  while  all  other  rays  undergo  more  or  less 
refraction.    A  secondary  axis  is  any  line  which 


A.  Piano  Convex. 

B.  Biconvex. 

C.  Periscopic  Convex. 


D.      Piano  Concave. 

K.      Biconcave. 

F.      Pei'iscopic  Concave. 


crosses  the  principal  axis  at  the  optical  center 
of  a  lens.  It  is  not  a  straight  line,  but  a  re- 
fracted one,  and  on  emerging  takes  a  direction 
parallel  to  that  which  it  would  have  pursued 
had  it  not  been  interrupted  by  the  lens.  Achro- 
matic L.,  a  lens  composed  of  two  pieces,  one  of 
crown  and  the  other  of  flint  glass;  the  former 
one  being  plus  and  the  latter  minus,  and  only 
half  as  strong  in  its  refractive  power,  but  of 
equal  dispersive  power,  and  overcomes  chro- 
matic aberration.  Aplanatic  L.  is  on  the  order  of 
the  achromatic  lens,  except  that  the  minus  is 
divided  and  placed  half  on  each  side  of  the  plus. 
In  this  way  not  only  the  chromatic  but  the 
spherical  aberration  is  overcome,  and  a  perfect 
lens  formed.  They  are  used  for  high-power  in- 
struments. Bifocal  L.  (see  Bifocal.)  Composite 
L.,  a  lens  having  three  features,  namely,  spher- 
ical, cylindrical,  and  prismatic.  Cylindrical  L.. 
a   lens  with  refractive  power  in  all  meridians 


OPHTHALMIC  DICTIONARY  12!) 

but  one.  This  one  is  known  as  the  axis,  and  is 
nothing  more  than  piano  glass.  The  refraction 
varies  from  zero  at  the  axis  to  the  full  strength, 
which  is  at  right  angles  to  the  axis.  Crossed  L., 
a  double-convex  lens  with  one  radius  equal  to 
six  times  the  other.  Crystalline  L.,  the  lens  of 
the  eye  which  resembles  a  crystal.  A  trans- 
parent double-convex  lens  situated  in  its  capsule 
behind  the  pupil,  between  the  aqueous  and  vit- 
reous humor,  and  when  in  a  state  of  rest  has  a 
focal  strength  of  from  plus  19  to  plus  20  diop- 
tries.  Compound  L.,  a  lens  consisting  of  two  or 
more  lenses  made  up  together,  such  as  a  sphere 
and  a  cylinder.  Torlc  L.,  a  lens  with  power  in 
all  meridians,  but  of  different  amounts  on  the 
same  side,  usually  made  extra  deep  periscopic. 
Fresnel  L.,  a  compound  lens  formed  by  placing 
around  a  central  convex  lens,  rings  of  glass  so 
curved  as  to  have  the  same  focus;  used,  espe- 
cially In  light  houses,  for  concentrating  light  in 
a  particular  direction.  Lenticular  L.  is  a  lens 
which  is  piano  at  the  edges,  and  the  power  is 
ground  in  a  space  of  about  half  an  inch  in 
diameter  in  the  center.  When  a  plus  lens  is 
required  it  is  made  in  the  form  of  a  scale  and 
cemented  on  a  piano  or  simple  cylinder.  In  this 
way  we  do  away  with  the  thick  edge  of  a  high- 
power  minus  lens,  and  it  also  makes  up  in  a 
thinner  form  for  a  high-power  plus,  but  they 
are  never  made  up  in  weak  lenses.  Orthoscopic 
L.,  a  lens  with  two  elements,  a  sphere  and  a 
prism,  so  arranged  that  the  amount  of  accom- 
modation and  convergence  used  should  exactly 
correspond.  Periscopic  L.,  a  lens  having  a  con- 
vex and  concave  surface.  Ret'roscopic  L.,  a  lens 
that  is  tilted  inward  at  the  top.  {ovKn> 


Toric  Lenses.  The  word  toric  was  taken  from 
the  word  torus,  which  means  in  architecture  the 
large  semicircular  molding  used  in  the  bases  of 
columns,  and  the  term  is  applied  to  a  lens  hav- 
ing curvature  in  all  meridians,  but  of  different 
amounts,  on  the  same  side  of  the  lens  with  its 
meridians  of  greatest  and  least  curvature  at 
right  angles  to  each  other.  The  meridian  of 
least  curvature  is  known  as  the  base  curve, 
while  the  other  side  of  the  lens  will  be  piano,  a 
concave  or  a  convex  sphere;  but  usually  made 
concave. 

To  give  an  idea  of  the  appearance  and  proper 
uses  of  such  lenses,  I  will  put  up  a  prescription 
for  one  of  the  five  subdivisions  of  ametropia 
which  can  be  corrected  by  lenses  in  toric  form. 
This  can  best  be  explained  by  diagrams. 

This  prescription  will  be  for  compound  hyper- 
opic  astigmatism  +  3.  sph.  ^  +  2.  cyl.  ax.  90. 


•^13 


/So' 


-f-S 


ho' 


This  lens  when  ground  must  refract  plus 
three  dioptries  in  the  ninetieth  and  plus  five 
dioptries  in  the  one  hundred  and  eightieth  me- 
ridians, independent  of  its  shape. 

But  in  order  to  get  a  deep  periscopic  effect, 
the  advantage  of  which  1  will  explain  later,  sup- 
pose we  grind  one  side  of  the  lens  thus: 


OPHTHALMIC  DICTIONARY  131 


rao' 


+3 


m 


The  difference  between  the  curvatures  in  the 
two  meridians  gives  us  the  desired  value  of  the 
cylinder,  and  on  the  other  side  we  will  grind  a 
minus  three  sphere,  which  will  neutralize  plus 
three  from  all  meridians,  leaving  the  lens  with 
the  required  strength.  In  this  lens  you  get  a 
plus  sphere  and  a  plus  cylinder,  and  at  the  same 
time,  if  a  cement  scale  is  required,  it  can  be 
placed  next  to  the  eye. 

When  a  toric  lens  is  desired,  it  is  not  neces- 
sary for  the  refractionist  to  mention  the  curva- 
ture. For  the  sake  of  simplicity,  just  write  the 
word  "toric"  beneath  the  description  of  the 
lenses  in  your  prescription.  Then  write  the  pre- 
scription in  the  usual  way. 

Toric  lenses  are  more  expensive  than  the  old 
form  of  lenses,  but  on  account  of  their  superior- 
ity they  are  coming  more  into  general  use. 

In  the  first  place,  they  allow  a  greatly  en- 
larged field  of  vision,  by  allowing  the  patient  to 
roll  the  eye  and  at  the  same  time  see  through 
the  edges  of  his  lens. 

With  lenses  of  the  ordinary  type,  when  an 
eye  turns  it  looks  obliquely  through  them  and 
obtains  a  prismatic  effect  that  is  not  desired, 
causing  the  image  to  be  more  or  less  distorted 
on  the  retina,  and  at  the  same  time  the  patient 


132 


LEWIS  POCKET 


is  bothered  with  reflection  from  the  back  of  the 
lenses  of  objects  on  the  side.  With  deep  peri- 
scopic  lenses  the  curve  coincides  approximately 
with  the  arc  formed  by  the  eye  in  turning,  and 


the  eye  is  looking  much  more  directly  through 
the  lens  and  obtains  a  much  larger  field  of 
vision  without  the  extra  prismatic  effect. 

The  diagrams  show  the  shape  of  the  two 
kinds  of  lenses  from  the  same  prescription, 
+  2  sph.  C  —  1  cyl.  ax.  90. 

Again,  the  edges  of  the  lenses  come  nearer  to 
the  face,  thus  adding  to  the  patient's  appear- 
ance. The  result  of  a  lens  of  this  description  is 
freedom  and  comfort  to  the  wearer,  so  much  so 
that  the  extra  cost  should  not  be  considered. 

When  a  cement  bifocal  is  required,  the  toric 
side  should  always  be  plus,  so  that  a  minus 
sphere  will  be  next  to  the  eye.  on  which  the 
scale  may  be  cemented. 
Lens  Capsule  (L.  a  lentile  +  dim.  of  capsa  =  box). 
A  transparent,  highly  elastic,  and  brittle  mem- 
brane which  encloses  the  crystalline  lens.  It 
rests  in  a  depression  of  the  vitreous  body  just 
behind  the  iris,  and  is  held  in  position  by  the 
suspensory  ligaments. 
Lentlconus     den-tik-o'-nus).      (L     lens -}- conus  = 


■Hfti-^^'*^- 


OPHTHALMIC  DICTIONARY  133 

cone.)  Exaggerated  curvature  of  the  crystalline 
lens. 

Lenticular  (L.  lenticula  =  a  lentlle).  Resembling 
a  lentil.   Lens-shaped;  pertaining  to  a  lens. 

Lenticular  Astigmatism.    See  Astigmatism. 

Lesion  (le'-shun).  (L.  loedere  =  to  injure.)  Any 
hurt,  wound,  or  local  degeneration. 

Leucoma  (lew-ko'-mah).     See  Leukoma. 

Leukoma  (lew-ko'-ma).  (Gr.  leukos  =  white.) 
White  corneal  opacity.    Albugo. 

Levator  (L.  levare  =  to  lift).  Elevator;  a  muscle 
raising  a  part. 

Levator  Palpebra  Muscle  (le-va'-tor  pal'-pe-bra 
mus'-l).     See  Muscles. 

Ligament  (lig'-a-ment).  (L.  ligare  =  to  bind.)  A 
tough  band  of  connective  tissue,  the  purpose  of 
which  is  to  connect  the  bones  together  or  sur- 
round them  as  a  capsule.  There  are  several  liga- 
ments concerned  in  the  anatomy  of  the  eye. 
Check  Ligament,  Ciliary  Ligament,  Palpebral 
Ligament,  External  Palpebral  Ligament,  Inter- 
nal Palpebral  Ligament,  Lockwood  Ligament, 
Suspensory  Ligament  or  Zone  of  Zinn,  Liga- 
ment of  Zinn.  The  Ciliary  L.,  or  circle  (annulus 
albidus),  is  the  bond  of  union  between  the  ex- 
ternal and  middle  tunics  of  the  eyeball,  and 
serves  to  connect  the  cornea  and  sclerotic,  at 
their  line  of  junction,  with  the  iris  and  external 
layer  of  the  choroid.  It  is  also  the  point  to 
which  the  ciliary  nerves  and  vessels  proceed 
previously  to  their  distribution,  and  it  receives 
the  anterior  ciliary  arteries  through  ^he  anterior 
margin    of    the    sclerotic.     A    minute    vasculd^r 


i::'.4  LEWIS  POCKET 

canal  is  situated  within  the  ciliary  ligament, 
called  the  ciliary  canal,  or  the  Canal  of  Fontana. 
from  its  discoverer.  Check  L.,  the  fibrous  bands 
attached  by  one  end  to  the  anterior  wall  of  the 
orbit  and  by  the  other  to  the  tendons  of  the 
recti  muscles.  Those  on  the  inner  side  are 
called  the  internal  check  ligaments,  and  those 
on  the  outer  or  temple  side  the  external  check 
ligaments.  The  action  of  these  ligaments  is  a 
normal  one.  They  prevent  or  retard  overaction 
of  the  abductors  or  adductors.  Lockwood  L., 
a  band  of  orbital  tissue  in  the  anterior  part  of 
the  orbit,  where  it  forms  a  hammock-like  band 
attached  at  one  end  to  the  lachrimal  and  at  the 
other  to  the  majar  bone.  Its  broader  central 
part  passes  below  the  eyeball  over  the  Capsule 
of  Tenon.  The  Palpebral  L.  joins  the  cartilage 
of  the  lids  to  the  orbit  the  same  as  the  tarsal 
ligament.  The  Externa!  Palpebral  L.  unites  the 
lid  to  the  outer  edges  of  the  orbit.  The  Internal 
Palpebral  L.  covers  an  area  including  the  upper 
maxilla  to  the  inner  margin  of  the  lid.  The 
Suspensory  L.,  or  Zone  of  Zinn,  surrounds  the 
crystalline  lens  and  holds  it  in  place  within  the 
circle  of  the  muscle  of  accommodation. 

Ligament  of  Zinn.  A  circular  ligament  which  is 
attached  to  the  bone  at  the  optic  foramen,  from 
which  arise  the  four  recti  muscles. 

Ligamentum  Pectinatum.  The  ligaments  which 
pass  from  the  base  of  the  iris  to  the  cornea. 
Through  its  meshes  pass  Fontana's  spaces. 

Light  (L.  lux  =  light").  Light  is  that  physical 
force  which,  after  entering  the  eye  and  acting 
upon  the  sensitive  elements  of  the  retina,  ex- 


OPHTHALMIC  DICTIONARY  135 

cites  in  the  mind  the  impression  of  vision  (or 
vibrations  of  ether).  It  is  an  extremely  rare, 
elastic  medium  which  is  diffused  over  the  uni- 
verse, emanating  from  the  sun  and  stars,  bodies 
in  a  state  of  ignition,  candle  flame,  electricity, 
etc.  It  is  said  to  travel  at  the  velocity  of 
186,000  miles  per  second  while  in  air.  Its  speed 
is  retarded  when  it  enters  a  denser  medium,  as 
water,  glass,  etc.  The  amount  of  the  retarda- 
tion depends  on  the  density  of  the  medium.  It 
regains  its  former  speed  on  emerging  into  air 
again.   The  unit  of  light  is  1  candlepower. 

Bodies  sending  forth  rays  or  waves  of  light 
are  called  luminous;  and  those  through  which 
it  passes  easily,  transparent;  those  through 
which  it  can  pass  less  easily,  translucent;  and 
those  through  which  it  cannot  pass,  opaque. 
When  light  meets  the  surface  of  a  body  it  may 
be  reflected,  absorbed,  refracted,  or  diffracted. 

It  is  the  cause  of  color  of  all  bodies,  being 
entirely  reflected  by  white  objects  and  absorbed 
by  black.  It  is  decomposed  in  passing  through 
a  prism,  and  its  seven  primary  colors  exposed, 
thus :  violet,  indigo,  blue,  green,  yellow,  orange, 
and  red.  Of  these,  violet  is  refracted  the  most 
and  red  the  least. 

Rays  of  light  that  do  not  enter  the  eye  are 
invisible.  A  ray  entering  a  darkened  room  is 
visible  because  the  floating  dust  reflects  some 
of  it  to  the  eye. 

White  light  is  the  combination  of  all  colors, — 
color  is  not  a  property  of  matter,  but  of  light, — • 
for  instance,  the  color  of  a  flower  is  its  property 
of  reflecting  to  the  eye  light  of  that  particular 
color,  the  other  colored  rays  being  absorbed. 
This  is  what  is  known  as  selective  absorption. 


136  LEWIS  POCKET 

Different  colored  light  has  different  wave 
length.  Red  has  the  longest  and  violet  the 
shortest  waves.  It  will  be  noted  that  violet 
must  travel  much  faster  than  red  in  order  to 
travel  with  it  through  space.  The  main  primary 
colors  are  red,  yellow  and  blue;  the  others, 
orange,  green,  indigo  and  violet,  -are  secondary 
or  "binary"  colors. 

In  moving  colored  objects  so  that  their  image 
moves  from  the  macula  to  the  periphery  of  the 
retina,  colors  grow  dim;  green  is  lost  first,  then 
red,  yellow  and  blue  last.  Color  blindness  is 
generally  congenital,  but  may  be  acquired  by 
changes  in  the  retina,  particularly  in  atrophy 
of  the  optic  nerve. 

From  an  optical  standpoint  there  are  two 
theories  of  the  way  in  which  light  travels, 
namely,  rays  and  waves. 

A  Ray  is  the  smallest  visible  line  of  light. 

A  Beam  is  a  collection  or  bundle  of  parallel 
rays. 

A  Pencil  is  a  number  of  converging  or  diverg- 
ing rays. 

Rays  emanating  from  an  illuminating  or  an 
illuminated  point  always  diverge;  in  nature 
there  are  no  converging  rays,  neither  are  there 
any  absolutely  parallel,  but  those  proceeding 
from  a  point  20  feet  or  farther  away  are  so 
nearly  so  that  the  difference  can  only  be  mathe- 
matically expressed,  and  for  the  purposes  of 
optics  are  considered  as  parallel.  According  to 
the  calculations  of  astronomers,  light  moves  at 
the  rate  of  about  186,000  miles  in  a  second; 
according  to  this,  it  requires  about  nine  minutes 
for  the  waves  of  light  from  the  sun  to  reach  the 


OPHTHALMIC  DICTIONARY  137 

earth,  and  those  from  the  nearest  fixed  star  are 
five  years  on  their  journey  before  tliey  reach  us. 

From  an  optical  standpoint  we  now  refer  to 
the  "Wave  Theory,"  and  in  order  to  do  this  it 
will  be  necessary  to  draw  somewhat  on  one's 
imagination.  You  have  ofttimes  noticed  when 
a  stone  is  dropped  into  a  calm  pond  of  water 
it  throws  forth  circular  waves  in  all  directions. 
The  first  or  nearest  wave  to  the  stone  will  have 
the  shortest  radius  of  curvature,  or,  in  other 
words,  the  greatest  strength  of  curvature.  As 
this  wave  spreads  it  will  decrease  in  curvature 
until  it  has  traveled  20  feet.  Beyond  20  feet  the 
waves  are  considered  plane,  meaning  by  this 
that,  when  on  account  of  the  pupil  of  the  eye 
being  about  an  eighth  of  an  inch  in  diameter, 
we  cut  from  a  wave  of  light  that  has  traveled 
20  feet  a  piece  one-eighth  of  an  inch  long,  that 
is,  the  amount  that  would  enter  the  eye,  it 
would  have  so  slight  a  curve  that  it  is  consid- 
ered to  have  none.  This  is  known  as  a  plane 
wave. 

The  word  minus  denotes  less;  the  farther  the 
wave  travels  from  its  center,  the  less  its  curva- 
ture; therefore  all  waves  that  are  going  from  a 
point  we  consider  minus,  and  for  the  sake  of 
simplicity  we  must  compare  the  waves  of  light 
with  the  waves  of  water,  and  instead  of  drop- 
ping the  stone  we  will  light  a  candle  that  will 
throw  off  waves  in  all  directions.  When  a  wave 
has  traveled  one-half  inch  from  a  point  it  has 
a  curve  of  minus  80,  because  it  has  a  radius  of 
curvature  of  one-eightieth  meter.  Now,  as  the 
one  and  same  wave  moves  on,  it  loses  its  curva- 
ture;  thus,  when  it  has  traveled  one  inch  from 


138  I.EWIS   POCKET 

its  center  its  curvature  is  less,  or  minus  40; 
and  at  two  inches,  minus  20;  three  inches, 
minus  13;  four  inches,  minus  10;  five  inches, 
minus  8;  twenty  inches,  minus  2;  forty  inches, 
minus  1;  eighty  inclies,  minus  .50  (these  figures 
are  the  fractional  part  of  a  meter,  which  the 
distance  represents) ;  twenty  feet,  no  curve,  or 
plane  wave.  Now,  if  one  will  stop  to  think,  he 
will  observe  these  figures  compare  with  the 
focal  length  of  lenses  in  the  trial  case;  that 
is  to  say,  a  wave  that  has  traveled  forty  inches 
from  a  point  is  known  as  a  minus  1,  and  a 
1-dioptry  lens  has  a  focal  length  of  forty  inches. 
A  wave  that  has  traveled  twenty  inches  from  a 
point  is  known  as  a  minus  2,  while  a  2-dioptry 
lens  would  focus  at  twenty  inches.  For  in- 
stance, you  may  ask  yourself,  "What  would  be 
the  curvature  of  a  wave  of  light  that  has  a 
radius  of  thirteen  inches?"  You  would  at  once 
think  of  the  dioptric  number  of  the  lens  that 
would  focus  at  thirteen  inches.  This  would  be 
a  3-dioptry.  Then  you  would  say  that  the  curve 
is  minus  3,  if  it  is  going  from  a  point,  but  if 
going  to  a  point,  plus  3.  You  will  notice  that 
in  referring  to  a  meter  it  is  spoken  of  as  forty 
inches.  There  is  a  difference  between  the  two, 
yet  it  is  near  enough  for  our  purpose,  and  saves 
the  trouble  and  inconvenience  of  working  with 
fractions;  so  far,  we  have  spoken  of  the  minus 
wave,  as  all  waves  in  nature  are  minus;  in 
order  to  have  a  plus  wave  we  must  use  arti- 
ficial means,  and  will  work  out  the  following 
example:  Place  a  lighted  candle  forty  inches 
from  a  plus  3  sphere;  considering  the  candle 
the  point  from  which  the  light  comes;  the  wave 


OPHTHALMIC  DICTIONARY  139 

has  traveled  from  a  point  forty  inches  before  it 
enters  the  lens,  therefore  it  enters  a  minus  1 
wave.  Minus  and  plus  neutralize.  If  more  plus 
than  minus  is  present  there  will  remain,  after 
neutralization,  an  amount  of  plus  equivalent  to 
the  difference.  Therefore  the  minus  1  will  go 
through  the  plus  3  sphere,-  and  will  emerge  a 
plus  2  wave,  and  focus  at  twenty  inches;  at  the 
focus  they  will  cross  and  begin  to  diverge,  or 
rather  become  minus. 

Light  travels  at  the  rate  of  186,000  miles  in  a 
second  while  in  air,  but  in  passing  through  a 
denser  medium,  such  as  glass,  its  speed  is  re- 
tarded according  to  the  density,  and  it  regains 
its  former  speed  on  emerging  into  air. 

It  always  depends  on  how  far  a  wave  is  from 
its  center  of  curvature  what  amount  of  curve  it 
will  have.    Study  the  following  examples: 


rttf 


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-;  ^©  o-'-'  bE  '  ^ 

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Ilihl^ffctiV^Vft^itti^ytif'T 


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4-4,     Cutoptry    MiiTor. 


OPHTHALMIC  DICTIONARY  143 

Light,  Recomposition  of.  The  reuniting  of  tlie 
colors  of  the  spectrum  so  as  to  produce  white 
light.  It  is  done  by  placing  a  second  prism 
exactly  like  the  first,  with  its  apex  turned  in  the 
opposite  direction.  The  light  will  be  recom- 
posed  and  will  emerge  from  the  second  prism  as 
white  light. 

Light  Area  on  the  Face.  The  term  used  to  desig- 
nate the  light  upon  the  face  when  the  bear.i  of 
light  from  the  retinoscope  is  directed  upon  the 
eye  under  observation. 

Light  Area  in  Pupil.  The  light  seen  in  the  pupil 
of  an  eye  under  observation  with  the  retino- 
scope, caused  by  the  reflex  from  the  retina.  Its 
character  and  relative  movement  indicate  the 
refractive  condition  of  the  eye. 

Limbus  (L.  border).    Edge;  border;  hem. 

Limbus  Cornea  (lim'-bus).  (Border  line.)  The  re- 
gion where  the  cornea  and  sclerotic  join. 

Limit  Angle.     See  Critical  Angle. 

Limitans  (lim'-it-ans).  (L.  limitare  =  to  limit.) 
That  which  limits  or  bounds  a  body  or  organ. 

Line  of  Fixation.  A  line  which  connects  the  ob- 
ject looked  at  with  the  macula  lutea  through 
the  nodal  point  of  the  eye. 

Line  of  Vision.  The  line  which  connects  the  object 
looked  at  with  the  fovea  centralis  (visual  axis). 

Lippitudo  (lip-pi-tu'-do).  (L.  lippus  =  blear-eyed.) 
An  inflammation  of  the  margins  of  the  eyelids. 

Liquor  Morgagni.  A  small  quantity  of  fluid  be- 
tween the  lens  and  its  capsule. 

Logadectomy  (log-ad-ek'-to-my).  A  removal  of  a 
part  of  the  conjunctiva  by  means  of  a  sharp 
knife. 


Logades  (log'-ad-ees).  (Gr.  logades  ^=  the  whites 
of  the  eyes.)     The  first  coat  or  tunic  of  the  eye. 

Logarithm  (log'-a-rithm).  (Gr.  logos  =  word + 
arithmos  =  number.)  The  exponent  of  the 
power  to  which  a  number  called  the  base  (in 
the  common  system,  10)  must  be  raised  to  pro- 
duce a  number 

Loimophtharmia.     Contagious  ophthalmia. 

Longitude  (lon'-ji-tud).  (L.  longus  =  long.)  The 
angle  at  the  pole  between  two  meridians,  one  of 
which,  the  Prime  Meridian,  passes  through  some 
conventional  point  and  from  which  the  angle  is 
measured. 

Long-Sightedness.     See  Hyperopia. 

Lorgnette  (lorn-yef).  Double  eye-glasses  attached 
to  a  handle.  This  term  is  often  applied  to 
opera-glasses. 

Louchettes.  A  kind  of  opaque  glasses  in  which, 
for  each  eye,  there  is  a  small  opening  which 
makes  it  impossible  to  look  in  any  other  way 
than  through  this  opening. 

Loxophthalmos  (lok-sof'-thal-mus).  (Gr.  loxos  = 
slanting  -j-  ophthalmos  =  eye.)  That  condition 
in  which  the  eye  is  turned  from  parallelism. 
(Strabismus;   Heterotropia.) 

Lucid  (L.  lucere  =^  to  shine).     Clear,  distinct. 

Lucifugal  (lu-sif'-u-gal).  That  condition  which 
exists  where  a  person  avoids  bright  light. 

Luminous  Bodies.  Those  sources  of  direct  light, 
as  the  sun,  a  lighted  candle,  etc. 

Luminous    Pupil.    The   appearance   of   the   pupil 

under  observation  with  the  retinoscope. 
Luxation    fluk  sa'-shun)    of  Lens    (L.   luxare  =  to 


OPHTHALMIC  DICTIONARY  145 

dislocate).  That  condition  where  the  crystalline 
lens  is  dislocated. 

Lymph  (L.  lympha  =  water).  A  transparent, 
slightly  yellow  liquid  which  fills  the  lymphatic 
vessels.  It  is  occasionally  rose  color  from  the 
presence  of  blood  corpuscles,  and  is  often 
opalescent  from  particles  of  fat.  L.  System  is 
a  collective  term  for  the  lymphatic  glands  and 
vessels. 

Lymphatic  (lim-fat'-ik).  Pertaining  to,  of  the 
nature  of,  containing,  or  conveying  lymph. 


M 


.ACRGPSIA  (mak-rop'-si-ah).  (Gr.  makros  = 
large  +  opsis  =  vision.)  That  condition  of  an 
eye  in  which  objects  appear  larger  than  they 
really  are. 

Macroscopic  (mak-ro-scop'-ic).  Gr.  makros  = 
large  +  skopeo  =  I  view.)  That  which  may  be 
seen  with  the  naked  eye. 

Macula  Lutea  (mak'-yu-lah  lew'-te-ah).  (L.  a  spot 
+  lutea  =  yellow.)  The  small  yellow  spot  of 
the  retina  which  lies  directly  in  the  visual  axis. 
It  is  about  4  mm.  to  the  temporal  side  of  the 
center  of  the  optic  disc,  on  the  horizontal  me- 
ridian, and  is  less  than  2  mm.  in  diameter.  A 
depression  in  its  center,  fovea  centralis,  is  the 
most  sensitive  point  of  vision. 

Madarosis  (mad-ar-o'-sis).  (Gr.  "bald.")  That 
condition  in  which  the  eyelashes  are  perma- 
nently destroyed. 

Maddox  Rod  (Ernest  E.  Maddox,  English  ophthal- 
mologist). An  opaque  disc  with  a  slit  through 
the  center.     Over  this  slit  is  placed  a  glass  rod 


JJJ^    \  \     AkJ       X     \_/\_^XVJJj  ± 


or  cylinder.     In  looking  through  this  rod  at  a 
small  round  light  it  causes  the  light  to  look  like 


Mafldox  Rod. 


a  long  streak.  This  rod  with  a  red  glass  disc 
over  the  other  eye  is  used  for  testiLg  muscular 
imbalance.  Before  testing  for  muscular  imbal- 
ance correct  all  errors  of  refraction. 

Madisterium  (mad-is-ter'-i-um).  An  instrument 
used  for  removing  the  eyelashes. 

Magnet  Operation.  A  method  used  for  removing 
particles  of  iron  and  steel  embedded  within  the 
tissue  of  the  eye,  by  means  of  a  magnet. 

Magnify  (mag'-ni-fy).  To  render  an  apparent  in- 
crease in  the  size  of  an  object  above  that  seen 
in  emmetropia. 

Malacia  (mal-a'-se-ah).  (Gr.  malakia  =  a  soft- 
ness.)    Morbid  softening  of  tissue. 

Malacocataracta  (mal-ak-o-kat-ar-ak'-tah).  A  soft 
cataract  which  forms  in  the  crystalline  lens  of 
a  person  under  the  fortieth  year.  This  form  of 
cataract  is  usually  the  result  of  injury. 


OPHTHALMIC  DICTIONARY  147 

Malaxation  (mal-ax-a'-shiin).  (L.  malaxare  =to 
sofren.)    A  rubbing  or  kneading  of  the  eyeball. 

Malignant  (mal-ig'-nant).  (L.  malus  =  evil.) 
"Destructive,  to  cause  distress."  A  term  ap- 
plied to  any  disease  whose  symptoms  are  such 
as  to  threaten  the  destruction  of  the  part.  See 
Myopia. 

Malingerer  (Fr.  malingre  =  sickly).  One  who  pre- 
tends to  have  a  defect  of  vision  or  some  other 
function,  to  evade  duty. 

Marginal  Keratitis  (mar'-jin-al  ker-at-i'-tis).  (L. 
margo  =  a  border.)  Relating  to  a  border  or 
edge.  A  disease  of  an  inflammatory  nature 
which  occurs  usually  in  elderly  people.  The 
inflammation  extends  around  the  rim  of  the 
cornea.  If  the  process  continues  the  cornea  is 
invaded  by  a  densely  vascular,  superficially 
ulcerated,  and  yet  thickened  zone. 

Marmarygea  (mar-mar'-ij-e-a).  (Gr.  "brilliant.") 
Appearance  of  sparks  before  the  eyes. 

Mass.  (Physics)  The  quantity  of  matter  which  a 
body  contains,  irrespective  of  its  bulk  or  volume. 

Mature  fma-tur').  (L.  maturare  =  to  ripen.) 
Fully  developed;  ripe. 

Means  (menz).  The  second  and  third  terms  of  a 
proportion. 

Measure  (mezh'-ur).  (L.  mensura  =  measure.)  A 
unit  or  standard  adopted  to  determine  the 
length,  volume,  or  other  quantity  of  some  other 
object. 

Media  (L.  medius  =  middle).  Intervening  bodies, 
such  as  glass,  air,  water,  etc.,  which  light  can 
pass  through  freely.    Media  is  plural  of  medium. 


Median  line,  ii.  A  line  perpendicular  to  and  bi- 
secting the  distance  between  the  centers  of 
rotation  of  the  eyes. 

Medium.      Intervening    body    or    quantity.      The 
dioptric  media  of  the  eye  consist  of  the  cornea,  I 
aqueous   humor,   crystalline   lens,   and   vitreous 
humor. 

Megalocornea  (meg-al-o-kor'-ne-ah).  fGr.  mcgas 
==  large.)  That  condition  in  which  there  is 
bulging  of  the  cornea. 

Megalopia  (meg-al-o'-pi-ah).  (Gr.  raegas  ^  great 
+  ops  =  eye.)     See  Macropsia. 

Megalopsia  (meg-al-op'-si-ah).  (Gr.  megas  =  great 
+  opsis  =  vision.)  That  condition  of  the  eye  in 
which  objects  appear  larger  than  they  really 
are. 

Meg'aloscope  (Gr.  megas  =  great  +  skopeo  =  I 
view).    A  large  magnifying  lens. 

Megascope  (meg'-a-skope).  A  microscope  for  ex- 
amining large  objects. 

Megophthalmus  (meg-of-thal'-mus).  (Gr.  megas  = 
great  +  ophthalmos  =  eye.)  That  condition  in 
which  the  part  of  eye  is  abnormally  large. 

Meibomian  Glands  (mi-bo'-me-an;  after  Meibo- 
mius,  the  discoverer).  A  variety  of  glands 
which  are  embedded  in  the  tarsal  cartilages. 
There  are  from  thirty  to  forty  in  the  upper  lid 
and  from  twenty  to  thirty  in  the  lower  lid. 
Their  ducts  open  upon  the  free  margin  of  the 
lids.  These  glands  secrete  a  sebaceous,  oily 
fluid  which  assists  in  lubricating  the  lids  as 
they  glide  over  the  eyeball,  and  also  prevents 
the  lids  from  sticking  together  when  we  have 
them  closed.     Another  function  is.  that  as  the 


OPHTHALMIC  DICTIONARY 


149 


margins  of  the  lids  are  kept  oily  at  all  times  the 
tears  do  not  flow  over  them  so  easily.  This  oily 
substance  also  mixes  with  the  tears  and  assists 


ANATOMY   OF  LIDS. 

To.  1.   Meibomian  Glands.  No.  5.   Orbicularis  Muscles. 

No.  2.   Puncta  Lachrymalia.      No.  6.   Lachrymal  Glands. 
Nos.  3  and  4.   Lachrymal  Canals. 

in  preventing  friction  between  the  eyeball  and 
lids,  and  at  the  same  time  prevents  the  cornea 
from  becoming  dry  so  quickly.  Also  known  as 
tarsal  glands.     See  Chalazion. 

f  MeTanin  (Gr.  melas  =  black).  A  dark  pigment 
from  choroid,  hair,  and  other  dark  tissues. 

^Melasma  (Gr.  melas  =  black).  Melanoderma; 
morbid  cutaneous  discoloration. 

I  Melasma  Palpebrarum  (mel-as'-ma  pal-pe-bra'- 
rum).  A  discoloration  of  the  eyelid,  which 
occurs  frequently  in  pregnant  women. 

'Membrana  Capsularis.  That  portion  of  the  ar- 
teria  centralis  which  forms  a  vascular  network 
and  coats  the  posterior  surface  of  the  lens. 


ave- 


150  LEWIS  POCKET 

Membrana  Pupillaris  (mem-bra'-na).  A  membrane 
covering  the  pupil  of  fetal  life.  This  some- 
times fails  to  disappear  up  to  time  of  birth. 

Membrane  (mem'-bran).  A  thin  tissue  covering 
some  surface  or  organ. 

Membrane  Nictitating  (L.  nictitare  =  to  wink). 
That  which  is  sometimes  called  the  third  eye- 
lid, to  be  seen  in  various  animals. 

Meniscus  (men-is'-kus).  (Gr.  meniskos  =  cres- 
cent.) A  crescent.  When  applied  to  a  lens, 
would  mean  that  it  is  more  periscopic  than 
necessary  to  produce  the  same  refracting  power. 

Menotyphlosis  (men-o-tyf-lo'-sis).  A  condition  of 
the  eye  in  which  there  is  diminution  of  vision 
during  night. 

Mensuration  (men-su-ra'-shun).  The  science  of 
measuring. 

Meramaurosis  (mer-am-au-ro'-sis).  A  condition  of 
the  eye  in  which  part  of  the  field  of  vision  is 
lost;  partial  amaurosis. 

Meridian  (mer-id'-i-an).  In  optics,  any  straight 
line  passing  from  edge  to  edge  on  the  surface 
of  a  lens  and  over  its  optical  center.  A  merid- 
ian of  the  cornea  is  any  straight  line  crossing 
its  surface  through  its  anterior  pole.  A  circle 
describes  360°,  one-half  of  which,  or  180°,  iS: 
marked  on  the  trial  frame.  0  and  180  are  found 
in  the  horizontal,  90°  describes  the  vertical. 
On  the  clock-dial  (astigmatic  chart)  they  are 
numbered  from  left  to  right,  which  must  be 
remembered  when  fitting  glasses,  and  on  trial 
frame  from  right  to  left.  These  figures  on  trial 
frame  correspond  with  clock-dial  when  they 
face  each  other. 


OPHTHALMIC  DICTIONARY  151 

Meropia    (mer-o'-pi-ah).      (Gr.   part,   vision.)      See 

Amblyopia. 
Mesoropter  (mes-o-rop'-ter).    The  position  of  eyes 

in  state  of  absolute  rest. 
Mesoseme    (mes'-o-sem).     (Gr.   mesos  =  middle + 

sema  =  sign.)     Having  a  medium  orbital  index 

between  84  and  89. 

Mesoretina  (mes-o-ret'-in-a).  (Gr.  mesos  =  mid- 
dle.)    The  middle  layer  of  the  retina. 

Metamorphopsia  (met-am-or-fop'-si-ah).  (Gr.  meta 
=  over  +  morphe  =  shape  +  opsis  =  vision.) 
That  condition  of  the  eye  in  which  objects 
appear  distorted. 

Metastasis  (met-as'-ta-sis).  The  shifting  of  the 
seat  of  a  disease  from  one  part  of  the  body  to 
another. 

Meter  (me'-ter).  (Gr.  metron  =  measure.)  Unit 
of  length  in  the  metric  system;  the  equivalent 
of  39.371  inches. 

Meter  Angle.  The  angle  through  which  each  eye 
turns  when  it  abandons  parallelism  of  the  bi- 
nocular lines  (orthophoria)  of  fixation  in  order 
to  fix  an  object  situated  upon  the  median  line 
one  meter  from  the  eye.  It  is  the  arc  embraced 
between  the  median  line  and  the  line  of  fixa- 
tion, whose  length  is  one  meter.  The  average 
distance  between  pupils  in  the  adult  is  62  mm.; 
then  one-meter  angle  equals  a  deviation  for  one 
eye  of  31  mm.  As  the  eyes  converge  closer  the 
meter  angles  increase  in  proportion.  This  de- 
scription refers  to  perfect  muscular  balance 
only.  The  writer  differs  from  other  authors, 
inasmuch  as  he  claims  that  if  the  eyes  were 
diverging    one    meter    angle    from    parallelism, 


:152  LEWIS  POCKET 

when  in  a  state  of  rest,  they  will  be  forced  to 
use  two  meter  angles  of  convergence  in  order 
to  view  an  object  one  meter  distant.  This  de- 
scription applies  to  the  different  varieties  of 
muscular  imbalance. 

Meter  Lens.  A  lens  that  will  focus  parallel  rays 
of  light  at  a  distance  of  one  meter. 

Metric  Curve.  A  curve  that  has  a  radius  of  one 
meter;  two  M,  C.  has  a  radius  of  20  inches. 

Metric  System.  A  decimal  system  of  weights  and 
measures  adopted  in  France  (1795)  and  various 
European  countries,  and  gradually  coming  into 
general  use  for  scientific  purposes.  Ten  units 
of  one  denomination  marking  one  unit  of  the 
next  higher.  A  m.eter  is  equivalent  to  about 
39.37  English  inches. 

Decimal  parts  of  the  standard  or  principal 
unit  are  denoted  by  Latin  prefixes;  multiples  of 
the  same,  by  Greek  prefixes. 

From  the  Latin  From  the  Greek 

Milli     means  0.001       Myria  means  10,000 

Centi    means  0.01         Kilo      means  1,000 

Deci     means  0.1           Hekto  means  100 

Deka    means  1 0 

In  the  tables  units  in  common  use  are  in  bold- 
faced type. 

Units  of  Length 

Standard  unit,  the  Meter 

Table 

10  millimeters  (mm.)  =  1  centimeter  (cm.) 
10  centimeters  =  1  decimeter  (dm.) 

10  decimeters  =  1  meter  (m.) 


OPHTHALMIC  Dictionary  i:.5 

10  meters  =  1  dekameter  (Dm.) 

10  dekameters  =1  hektometfer  (Hm.) 

10  hektometers  =  1  kilometer  (Km.) 

10  kilometers  =1  myriameter  (Mm.) 

Microblepharia  (mi-ki-o-blef-a'-ri-ah).  (Gr.  mikro^ 
=  small  +  blepharon  =  eyelid.)  A  very  narrow 
and  thin  eyelid. 

Microcornia  (mi-ki'o-k5t''-iie-ali)*  (Gr.  mikros  =^ 
small.)     A  small  coriiea. 

Microlentia  (mi-kro-len'-ti-ah)i  A  very  small  crys- 
talline lens. 

Micrometer  (Gr.  mikros  ==  stiiall  +  metron  =' 
measure).  An  instrument  which  is  used  for 
making  measurements  of  very  small  bodies. 

Microphtlialmia  (my-krof-thal'-mee-ah).  (Gr.  mi- 
kros =  small  +  ophthalmos  =  eye.)  Abnormally 
small  eyes. 

Micropsia  (my-krop'-see-ah).  (Gr.  mikres  ^^ 
small  +  opsis  =  sight.)  That  condition  of  th^ 
eye  in  which  objects  appear  smaller  than  they 
really  should. 

Microscope  (mi'-kro-scope).  (Gr.  mikros  =  small 
+  skopeo  =  I  view.)  An  optical  instrument 
used  for  examining  minute  objects. 

Migraine  (mi-gran')-  (Gr.  hemi  =  half  4-  kranion 
=  skull.)  A  kind  of  sickness  or  nervous  head- 
ache, usually  periodical  and  confined  to  the  side 
of  the  head. 

Mikron  (mi'-kron).  (Gr.  mikros  =  small).  Mil- 
lionth part  of  a  meter. 

Milium  (L.  millet  =  seed).  A  small  elevation,  on 
the  skin  of  the  eyelid,  filled  with  a  greasy 
secretion. 


Milphae  (mil'-phae).  A  morbid  condition  in  which 
clie  eyelashes  drop  out.  . 

Milphosis  (mil-fo'-sis).  That  condition  in  which 
the  eyebrows  as  well  as  the  eyelashes  have 
fallen  out. 

Minify  (min'-i-fy).  To  render  an  apparent  de- 
crease in  the  size  of  an  object  from  that  seen  in 
emmetropia. 

Minuend  (min'-u-end).  (L.  minuere  =  to  lessen.) 
The  number  from  which  another  num.ber  is 
subtracted. 

Minus  (mi'-nus).  Less:  that  from  which  some- 
thing has  been  subtracted;  negative;  as,,  a 
minus  quantity.  Minus  lenses,  same  as  con- 
cave. 

Miosis  (mi-o'-sis).  (Gr.  meiosis  =  a  lessening.) 
Excessive  contraction  of  the  pupil. 

Miotic  (mi-ot'-ic).  Any  agent  or  medicine  which 
causes  the  pupil  to  contract. 

Molecule  fmol'-e-kul).  The  smallest  particle  of 
any  substance. 

Molluscum  (mol-us'-kum).  (L.  mollis  ^  soft.)  A 
skin  disease  with  pulpy  tumors,  chiefly  on  the 
face,  neck,  and  trunk,  due  to  altered  gland 
secretion.  A  small  pearly,  warty  elevation 
which  breaks  down  in  the  center  and  discharges 
a  cheeselike  material.  It  is  said  to  be  con- 
tagious. 

Momentum  (mo-men'-tum).  (L.  momentum  =  mo- 
tion.) The  quantity  of  motion  in  a  moving 
body,  being  always  proportioned  to  the  quantity 
of  matter  multiplied  into  the  velocity. 

Monoblepsis  (mon-o-blep'-sis).  (Gr.  monos  =  one 
+  blepsis  =  sight.)      That    condition    in    which 


OPHTHALMIC  DICTIONARY  155 

objects  are  seen  distinctly  only  when  the  eyes 
are  used  singly,  vision  being  imperfect  when 
both  eyes  are  used. 

Monochromatic  Light  (Gr.  monos  ^  single + 
chroma  =  color).  The  spectrum  is  formed  by 
a  prism  dividing  light  into  its  seven  colors. 
Such  light  is  called  Monochromatic  Light. 

Monocle    (mon'-o-kl).      An    eyeglass    to    be    worn 

over  one  eye  only. 
Monocular    (mon-ok'-u-lar).      (Gr.   monos  ==  single 

+  L.    oculus  =  eye.)      Having    one    eye    only. 

Monocular  vision   is   that   condition   where  the 

patient  has  vision  in  one  eye  only. 
Monoculus.    A  monster  with  one  eye  only. 
Moon-Blindness.    Amblyopia  caused  by  having  the 

eyes  exposed  to  the  full  ^lare  of  the  moon  for 

considerable  time. 
Monoparesis     (mon-o-par'-es-is).       (Gr.     monos  =^ 

single  +  paresis.)     Paralysis  of  a  single  part  of 

the  body. 
Monopathy   (mon-op'-ath-e).     (Gr.  monos  =  single 

+  pathos  =  suffering.)     A  local  disease  of  one 

organ  or  function. 
Monops    (mon'-ops).      (Gr.    monos  =  single -f  ops 

-=  eye.)     A  foetus  with  but  one  eye. 
Motor  (L.  "a  mover").    A  nerve  center  controlling 

motion.    A  muscle  causing  motion. 
Motor    Muscles.      The    muscles    that   control   the 

movements  of,  or  parts  of,  the  eyes — the  recti, 

the   oblique   muscles,   the   ciliary,   and    the   iris 

muscles. 
Mucocele   (mu'-ko-sele).     (L.  mucus  +  Gr.  kele  =^ 

tumor.)    Distention  of  the  lachrymal  sac,  chronic 


thickening  of  the  lining  membrane,  and  in- 
creased secretion  of  mucus.  The  mucus  may  be 
clear  or  turbid.    Any  tumor  containing  mucus. 

jVIuscae  Volitantes  (mus^-cae  vol-i-tan'-tes).  (L. 
"flying  flies.")  Small  floating  bodies,  resem- 
bling sticks,  etc.,  which  move  about  in  the  field 
of  vision,  but  do  not  actually  cross  the  fixation 
point,  and  never  interfere  with  sight.  They  are 
usually  seen  against  some  bright  object.  They 
depend  upon  ipinjite  changes  in  the  vitreous, 
which  are  present  in  nearly  ^11  eyes.  They 
vary,  or  seem  to  vary,  greatly  with  the  health 
and  state  of  the  circulation,  but  are  of  no  real 
importance.  They  are  most  abundant  and 
troublesome  in  myopic  eyes. 

Muscle  (L.  musculys  =:  a  little  mouse,  from  the 
resemblance  of  a  muscle  in  contraction  to  the 
movements  of  a  mouse  under  a  cloth).  Muscles. 
(Eye)  The  eyeball  is  rotated  around  its  center 
of  rotation  by  the  individual  pr  combined  action 
of  six  muscles,  namely,  four  recti  or  straight, 
and  the  two  oblique;  the  seventh  muscle,  leva- 
tor palpebrae,  is  attached  jtp  the  upper  lid, 
which  it  raises. 

Of  the  six  muscles  inserted  into  the  eyeball, 
five  take  their  origin  from  the  apex  of  the 
orbit,  while  the  sixth  and  shortest,  the  inferior 
oblique,  takes  its  origin  from  the  superior  max- 
illary bone  at  the  anterior  and  nasal  side  of  the 
orbit. 

Internal  Rectus  Muscle  turns  tjie  eye  in,  ^nd 
is  supplied  by  the  third  cranial  or  motor  oculi 
nerve. 

Superior  Rectus  Muscle  turns  the  eye  up,  and 


OPHTHALMIC  DICTIONARY  157 

is  supplied  by  the  third  cranial  or  motor  oculi 
nerve. 

Inferior  Rectus  Muscle  turns  the  eye  down, 
and  is  supplied  by  the  third  cranial  or  motor 
oculi  nerve. 

Inferior  Oblique  Muscle  rolls  the  eye  on  its 
optic  axis,  drawing  the  bottom  and  back  part  of 
the  eye  in  and  down  while  the  front  moves  up 
and  out,  and  is  supplied  by  the  third  cranial  or 
motor  oculi  nerve. 

External  Rectus  Muscle  turns  the  eye  out, 
and  is  supplied  by  the  sixth  cranial  or  abducens 
nerve. 

Superior  Oblique  Muscle  rolls  the  eye  on  its 
optic  axis,  turning  the  back  part  of  the  eye 
inward  and  upward  while  the  front  part  moves 
down  and  out,  and  is  supplied  by  the  fourth 
cranial  or  patheticus  nerve. 

Ciliary  Muscles  are  inside  the  eyeballs,  and 
are  used  for  accommodating  only.  They  are 
supplied  by  the  third  nerve. 

Orbicularis  Palpebrarum  Muscle  closes  the 
lids,  and  is  supplied  by  the  seventh,  or  facial 
nerve.     (One  of  the  muscles  of  expression.) 

Levator  Palpebra  Superioris  lifts  the  lids,  and 
is  fed  by  a  branch  of  the  third  cranial  nerve. 

Sphincter  Muscle,  which  closes  the  pupil,  is 
supplied  by  the  third  nerve. 

Radiating  Muscles  of  the  iris,  which  dilate 
the  pupil,  are  supplied  by  the  sympathetic 
nerve. 

Horner's  Muscle.     See  Tensor  Tarsi. 

Palpebral  Muscles  are  two  involuntary  mus- 
fles,  superior  and  inferior.  The  superior  is 
principally  inserted   into   the  upper   margin   of 


the  tarsal  plate.  The  inferior,  found  in  the 
lower  lid,  interwoven  with  the  fasciculi  of  the 
orbicularis  palpebrarum. 

Riolan's  Muscle  is  the  muscular  tissue  sur- 
rounding the  hair  follicles  and  glands  of  Moll, 
near  the  border  of  the  eyelids. 


P5 


Tensor  Tarsi  compresses  the  lachrymal  sac 
and  pulls  the  puncta  against  the  eyeball.  Sup- 
plied by  the  seventh  cranial  nerve. 

Corrugator    Supercilii    draws    eyeorow    down 


OPHTHALMIC  DICTIONARY 


159 


and    inward,    and    is    supplied    by    the    seventh 
facial  nerve. 


Cut  showing  the  Extrinsic  Muscle. 


Fyramidalis  nasi.     This  muscle  depresses  the 
eyebrow.     Supplied  by  the  seventh  facial  nerve. 


MuHer's  Muscle.  Bands  of  circular  fibers  sit- 
uated internal  to  the  radiating  muscles  in  the 
ciliary  body.  They  are  sometimes  called  the 
"ring  muscle"  of  Muller.  Fibers  of  Mullen  are 
the  radiating  fibers  which  pass  through  nearly 
the  entire  thickness  of  the  retina,  supporting  its 
different  layers  and  binding  them  together. 
They  form  at  one  end  the  membrana  limitans 
interna  and  at  the  other  end  the  externa. 

Muscular  Asthenopia.    See  Asthenopia. 

Muscular  Imbalance.  It  is  generally  agreed  by 
the  authorities  of  today  that  ametropia  is  re- 
sponsible for  90  per  cent  of  Muscular  Imbalance. 
For  this  reason  it  is  considered  advisable  to 
always  correct  any  ametropia  that  may  be  pres- 
ent, and  have  the  patient  wear  the  correction 
for  at  least  six  weeks.  At  the  end  of  this  time, 
should  any  muscular  imbalance  be  manifest, 
correct  half  of  the  amount.  Always  test  for 
muscle  trouble  while  the  patient  is  wearing  his 
full  correction  for  the  ametropia,  otherwise  it 
will  not  be  considered  a  proper  test.  There  are 
but  few  exceptions  to  this  rule:  e.  g.,  when  a 
prism,  base  in,  will  allow  you  to  decrease  a 
minus  lens  or  increase  a  plus,  prescribe  it.  See 
Heterophoria  and  Heterotropia. 

Mycophthalmla  (mi-kof-thaK-mi-ah).  Inflamma- 
tion of  the  conjunctiva,  caused  by  a  spongy 
growth. 

Mydriasis  (mid-ri'-as-is).  Dilatation  of  the  pupil, 
caused  by  the  use  of  atropine  or  other  mydriat- 
ics, or  paralysis  of  the  motor  oculi  nerve. 

tVlydriatic  (mid-ri-at'-ic).  A  drug  that  dilates  the 
pupil. 


OPHTHALMIC  DICTIONARY  161 

Myiocephalon  (my-i-o-sef'-al-on).  (Gr.  myia  ==  fly  -;- 
kephale  =  head.)  A  small  protrusion  of  the  iris 
through  a  perforation  of  the  cornea. 

Myitis  (mi-i'-tis).  (Gr.  mys  =  muscle  -|-  itis  =  in- 
flammation.)    Inflammation  of  the  muscles. 

Myodesopsia  (Gr.  myia  =  fly  -|-  opsis  =  sight).  See 
Muscae  Volitantes. 

Myograph  (ray'-o-graph).  (Gr.  mys  =  muscle + 
grapho  =  I  register.)  An  instrument  for  record- 
ing the  different  phases,  such  as  the  velocity, 
intensity,  etc.,  of  a  muscular  contraction,  with 
the  aid  of  a  registering  apparatus. 

Myography  (my-og'-ra-phy).  (Gr.  mys  =  muscle  + 
graphe  =  a  drawing.)  A  description  of  muscles, 
including  the  study  of  muscular  contraction, 
with  the  aid  of  a  registering  apparatus. 

Myology  (my-ol'-o-ji).  (Gr.  mys  =  muscle  -|-  logia 
=  a  discourse.)  A  description  of  the  muscles 
of  the  human  body. 

Myologist  (my-ol'-o-gist).  One  skilled  in  that  part 
of  anatomy  which  treats  of  muscles. 

Myope  (my'-ope).   A  near-sighted  person. 

Myopia  (my-o'-pi-ah).  (Gr.  myo  =  close -f- ops  = 
eye.)  An  optical  defect  of  the  eye  which  causes 
parallel  rays  of  light  to  focus  in  front  of  the 
retina,  with  the  muscles  of  accommodation  at 
rest.  It  is  also  known  as  Brachymetropia  and 
Hypometropia.  A  correction  (concave  lens)  is 
necessary  before  normal  vision  can  be  obtained. 
In  the  early  days  the  Greeks  noticed  that  all 
near-sighted  persons  could  see  better  at  a  dis- 
tance by  half  closing  the  eyelids  (squinting). 
hence    the    name    myopia.     The    eyeball    may 


be  too  long  (axial)  or  the  refraction  too  great, 
causing  the  parallel  rays  to  cross  and  meet  the 
retina  as  divergent  rays,  which  form  a  circle  of 
diffusion,  and  so  cause  a  blurred  and  indistinct 
image  of  the  object.  Myopia  from  excess  of 
curvature  is  much  rarer  than  the  axial  form. 
We  sometimes  see  a  case  of  apparent  myopia 
due  to  excess  of  curvature  of  the  lens,  caused 
by  a  spasm  of  the  ciliary  muscle.  This  is  what 
is  known  as  false  myopia,  and  will  disappear 
under  the  iuiluence  of  atropine,  or  rest. 


These  cuts  have  not  been  made  with  mathematical  pre- 
cision, but  are  merely  intended  to  roughly  exemplify  the 
principle  involved.  The  above  Mlustratts  the  effect  of  a 
distant  point  upon  a  myopic  eye.  It  will  be  observed  that 
the  rays  from  the  distant  point  cause  the  image  from  that 
point  to  spread  out  over  a  considerable  area  on  the  retina. 
A  million  points  would  make  a  million  blurred  spots. 
They  would  overlap  each  other  and  render  the  picture 
indistinct. 

Bonders  pronounced  every  highly  myopic  eye 
a  diseased  eye,  but  of  late  years  it  has  been 
shown  that  this  remark  is  liable  to  convey  a 
false  meaning.  It  is  admitted  that  up  to  3-D. 
the  cases  are  seldom  serious,  it  being  generally 
possible  to  give  perfect  vision  by  proper  glasses, 
but  when  the  case  is  above  5-D.  we  do  not 
always  obtain  perfect  vision  by  proper  lenses, 
and  look  for  vari'^us  patholcgical  conditions. 


OPHTHALMIC  DICTIONARY  163 

Symptoms:  The  patient  sees  distant  objects 
badly  and  near  objects  better.  The  pupils  are 
usually  large,  and  as  presbyopia  advances  they 
contract.  The  ciliary  muscles  are  smaller  and 
weaker  than  in  the  normal  or  emmetropic  eye. 
As  a  rule,  myopic  patients  cannot  wear  their 
full  correction  when  first  fitted,  but  after  wear- 
ing about  two-thirds  of  the  correction  for  about 
six  weeks  the  full  amount  may  be  prescribed. 
Myopia  that  is  gradually  on  the  increase  is 
called  Progressive  Myopia.  Myopia  that  is  of  a 
rapidly  progressive  type,  and  is  very  destructive 
to  the  tissues  of  the  eye,  is  called  Malignant 
Myopia. 

Myopic  Crescent.  As  seen  by  the  ophthalmoscope. 
is  a  white  crescent  at  the  outer  side  of  the  optic 
disc.  This  condition  is  caused  by  the  choroid 
being  torn  away  from  the  optic  disc  and  allow- 
ing the  sclerotic  to  show  through.  Found  in 
high  degrees  of  myopia. 

Myosis  (my-o'-sis).  (Gr.  myo  =  I  close  the  eye.) 
Abnormal  contraction  of  the  pupil.  (Same  a^ 
Miosis.) 

Myositis  (my'-o-si'-tis).  (Gr.  mys  =  muscle  +  itis 
=  inflammation.)     Inflammation  of  the  muscles. 

Myotic.  (Gr.  myo  =  I  close  the  eye.)  An  agent 
that  will  contract  the  pupil,  such  as  eserin, 
pilocarpine,  etc. 

Myotomy  (mi-ot'-o-me).  (Gr.  my s  =  muscle -f- 
tome  =  a  cutting.)  The  dissection  or  division  of 
muscles. 


N 


ASAL  DUCT  (L.  nasus  =  nose -f  ducere  =  to 
lead).  That  part  of  the  tear  duct  which  extends 
from  the  lower  part  of  the  lacrimal  sac  to  the  in- 
ferior canal  of  the  nose.  It  is  about  five-eighths 
of  an  inch  in  length  and  lined  with  a  mucous 
membrane  similar  to  the  lacrimal  canals.  At 
the  end  of  the  duct  we  find  the  valve  of  Hasner. 

Near  Point  (or  Punctum  Proximum).  The  nearest 
point  at  which  the  eye  can  see  distinctly  when 
employing  its  full  amount  of  accommodation. 
It  varies  with  the  amount  of  accommodation  the 
eye  possesses.  The  way  to  determine  the  near 
point  is  to  note  the  shortest  distance  at  which 
an  emmetrope  can  read  small  print  with  each 
eye  separately.  Properly  speaking,  the  near 
point  is  that  point  for  which  the  eyes'  refrac- 
tion is  adjusted  when  the  full  amount  of  accom- 
modation is  being  used. 

Near-Sight.    See  Myopia. 

Neb'uia  (L,  "cloud").     Slight  corneal  opacity. 

Needling  (need'-ling).  An  operation  for  soft  cata- 
ract. The  lens  capsule  is  needled,  and  the 
aqueous  allowed  to  absorb  the  lens. 

Negative  (neg'-a-tive).  (L.  negare  =  to  deny.) 
The  opposite  of  positive.  The  negative  surface 
of  a  periscopic  lens  is  the  concave  surface. 

Neonatus  (ne-on-a'-tus).  (Gr.  neos  =  new  +  L,  na- 
tus  =  born.)    Newly  born. 

Neotocophthalmia  (ne-ot-ok-of-thar-mi-ah).  See 
Ophthalmia  Neonatorum. 

Nephablepsia  (nef-ab-lep'-si-ah).  See  Snow- 
Blindness. 


OrHTHALMIC  DICTIONARY  165 

Nepheiopia  (nef-el-o'-pi-ah^.  (Gr.  nephele  =  cloud 
+  ops  ■=^  eye.)  A  diminution  of  vision,  caused 
by  a  cloudiness  of  the  transparent  parts  of  the 
eye. 

Nephritic  Retinitis  (nee-frit'-ik).  A  form  of  in- 
flammation of  the  retina  associated  with  Brights 
disease  of  the  kidneys,  characterized  by  white 
streaks  along  the  course  of  the  blood-vessels. 

Nerve  CL.  nervus  =^  nerve).  A  white  string-like 
fiber  which  transmits  impressions  from  an  organ 
to  the  brain  or  from  the  brain  to  an  organ. 
Cranial  N.,  any  nerve  arising  from  the  brain 
direct.  There  are  twelve  cranial  nerves,  as 
follows : 

1.  Olfactory,  special  sense  of  smell. 

2.  Optic,  special  sense  of  sight  (retina). 

3.  Motor  Oculi,  motor  nerve  for  eye  muscles. 

4.  Patheticus,    motor   nerve   for   superior   ob- 
lique muscle. 

5.  Trigeminus,  sensory,  motion,  and  taste. 

6.  Abducens,  motor  nerve  for  external  rectus 
muscle. 

7.  Facial,  motor  nerve  for  muscles  of  face. 

8.  Auditory,  special  sense  of  hearing. 

9.  Glosso-Pharyngeal,  sensation  and  taste. 

10.  Pneumogastric,  sensation  and  motion. 

11.  Spinal  Accessory,  motion. 

12.  Hypoglossal,  motor  nerve  of  tongue. 

The  nervous  system  is  a  system  of  connection 
and  communication  by  which  the  different  or- 
gans, vessels,  and  various  parts  of  the  body  are 
brought  into  direct  relation  with  each  other  and 
with  the  mind,  and  the  various  organs  stimu- 
lated  to  harmonious  or  alternating  action.     It. 


consists  of  the  brain  and  spinal  cord,  called  the 
central  nervous  system,  which  controls  the  vol- 
untary actions  of  the  body,  sometimes  called 
the  nerves  of  animal  life,  and  is  directly  con- 
nected with  the  sympathetic  nerves,  which  have 
been  termed  nerves  of  organic  life,  they  being- 
involuntary  nerves  and  control  the  involuntary 
action  of  the  various  vital  processes  of  the 
body.  The  nervous  system  is  divided  into  the 
cerebro-spinal  or  central,  sympathetic,  and  the 
vaso  motor.  The  vaso  motor  system  is  a  part 
of  the  sympathetic  system  and  consists  of  the 
vaso  motor  center  located  in  the  medulla  ob- 
longata; of  certain  other  subsidiary  vaso  motor 
centers  in  the  spinal  cord,  and  of  vaso  motor 
nerves.  This  system  is  connected  with  the 
blood-vessels  in  the  various  parts  of  the  body, 
the  muscular  coats  of  which  are  supplied  with 
filaments  and  plexuses  of  vaso  motor  nerves 
which  regulate  the  size  of  the  blood-vessels. 
They  are  of  two  kinds:  vaso  dilators,  stimula- 
tion of  which  causes  dilatation  of  the  blood- 
vessels and  an  increased  amount  of  blood  to  a 
part,  and  vaso  constrictors,  stimulation  of  which 
causes  constriction  or  contraction  of  the  blood- 
vessels and  a  diminished  amount  of  blood  to  a 
part.  This  last  named  system  is  very  important 
to  the  practitioners  of  manipulatory  forms  of 
healing,  and  has  only  in  the  past  few  years 
been  known  to  any  extent,  the  vaso  motor  cen- 
ter being  discovered  by  Schiff  in  1855,  and  more 
accurately  localized  by  Ludwig  in  1871.  The 
cranial  nerves  are  those  that  have  their  appar- 
ent origin  in  the  cranium.  Sommering  and 
other  European  anatomists  name  twelve  pairs, 


OPHTHALMIC  DICTIONARY  167 

while  Willis  and  a  few  other  authors  designate 
only  nine  pairs,  according  to  the  order  in  which 
they  pass  out  of  the  base  of  the  brain. 

Motor  N.,  one  which  contains  wholly  motor 
fibers.  N.  Center,  a  group  of  cells  which  con- 
sist of  gray  matter  and  have  a  common  func- 
tion. Mixed  N.,  a  nerve  which  is  both  motor 
and  sensory.  N.  Head,  the  optic  disc  or  papilla. 
Sensory  N.,  any  nerve  which  transmits  sensa- 
tions or  impulses.  Sympathetic  N.,  any  nerve 
of  the  sympathetic  system. 

Optic  Nerve.  The  nerve  which  transmits  ret- 
inal sensations  from  within  the  eye'  to  the  brain, 
and  is  known  as  the  second  cranial  pair. 

The  Nerve  of  Vision.  It  is  about  5  cm.  in 
length  and  may  be  spoken  of  in  three  ways — 
the  intracranial,  the  intraorbital,  and  the  intra- 
ocular. 

The  optic  nerves  are  noticeable  for  their  size 
and  their  running  a  longer  course  within  the 
cranium  than  within  the  orbit,  and  that  they 
furnish  no  branches  from  their  origin  to  their 
termination. 

Transverse  sections  of  the  optic  nerve  show 
it  to  be  composed  of  about  eight  hundred  dis- 
tinct bundles  of  nerve  fibers,  separated  from 
each  other  by  connective  tissue  from  the  pia 
mater.  The  entire  number  of  fibers  contained 
within  the  optic  nerve  probably  approaches  a 
half  million.  These  fibers  after  entering  through 
the  lamina  cribrosa  (sieve-like  opening)  again 
pass  through  the  choroidal  fissure  (hole  in  cho- 
roid) and  spread  out  in  such  a  way  as  to  form 
the  shape  of  a  wineglass  (the  retina)  The 
fibers  thems-elves  are  not  rensitive  to  light,  but 


each  one  terminates  in  a  sensitive  point  (rods 
and  cones)  and  in  all  parts  of  the  third  tunic 
(the  retina),  except  at  ihe  entrance  of  the  optic 
nerve  (optic  disc).     See  Retina:   Optic  Tract. 


IIKAD    UF    Tlii.    '^'r: 


m:kve. 


D.  Ophihiilmoscopic  view  of  the  Optir  Disc.  The  sniiiH 
excavations  seen  around  the  cM-nter  is  the  Lamina 
•  'riljroHa.  The  I'apilla  Is  encir«l»il  by  th<"  white  ScKral 
HIiiK   (<•»    also  the   dark   Choroidal   HInK   niarke«l    (d) 

i;.    KonK'tudlnal    S«  ttlon    of    H«  a»l    of    Dptif    N«Tve ;    r,    tl»<* 
Iteiiiia;     b.     (Jptic     I0x(avatl«>n     and     Canal     for    Central 
Art<ry     (porous    optlrust;     rh.     the    fliorold;     E.     Opil< 
Nerve;    e.    Ihe   narrow    Interspace    whic  li    lorrespondn    t 
the  Sidrral    HlnR  »ei  n    by    the   Op)itliahuoscope;    s.   Scb 
rotir:   I  I,    Entrance   of  short    Ciliary    Artery. 

Neurasthenia  (nu-ras-thon-i'-ah).  (Gr.  neuron  — 
nerve  I  astheneia  weakness.)  Exhaustion  of 
nerve   force. 

\ 


tt  « 


orill'HAl.AIh  '    I  )H'l  1(  •XAKV 


1G9 


Neuritis    (iieu  ri'-tis).      (dr.   lU'uron       nerve   f  itis 
iiitlaininatioiij       Intlanimatioii    of    the    optic 

nerve. 
Neurology   (  nu  rol'-o-je).        (CJr.  neuron       uerve -f 

loiAJa       discourse.)       A    study    ol    the    nervous 

svstem. 


\li:\V     OF     THK     KYK     FROM     THK     TE.VIPORAI.     .mDF 

WITH  l'.\KT  OF  THE  ORBIT  REMOVED. 
1  Eyj'biiM  with  part  of  e.xternal  rectus  muscle.  li. 
Superior  Maxilla.  3.  Thlril  pair  (or  Motor  Ocull)  nerve.s. 
Th.y  art-  di.strlbutt-d  to  all  the  mu.sclts  of  the  eye.  except 
the  Supirior  obiiijue.  External  Rectu.s  and  the  Dilator 
.Mu.sili-s  of  the  Iri.s.  4.  Fourth  pair  of  Nerves,  feeding 
Superior  oblique  Muscle.s.  (J.  Sixth  pair  of  Nerves,  feed- 
iiiK   External    Rfctu.-s.      8.    t'lllary  Nerves  entering  the  globe. 

Neurcdealgia.  T'ain  or  excessive  sensibility  of 
the  retina. 

Neurodeatrophia.     Atrophy  of  the  retina. 

Neuroretinitis  ( neu-ro-ret-in-i'-tis).  ((Jr.  neuron  =^ 
nerve  4-  L.  retina  -f-  Gr.  itis.)  Intlannnation  of 
tlie  optic   nerve  and  retina. 

Neutralize  (^neu'-tral-ize).  (L.  neuter  neither.) 
'!  ht>  method  of  counterbalancing  or  doing  away 
with  power  in  lenses.  In  order  to  determine 
whether  a  lens  is  of  plus  or  minus  power,  hold 
i;    up  a   few    inches   from    the   eye  and   look   at 


some  distant  object  through  it,  then  move  the 
lens  from  side  to  side  and  if  the  object  appears 
to  move  in  the  opposite  direction  to  the  move- 
ment of  the  lens  it  is  a  plus  lens.  If  you  wish 
to  find  its  dioptric  power,  take  from  your  trial 
case  a  minus  lens  and  put  them  together  and 
again  look  through  them  at  the  object,  and 
should  the  object  still  move  against  the  move- 
ment of  the  lenses  the  minus  is  not  strong 
enough.  On  the  other  hand,  should  the  move- 
ment be  reversed  and  now  the  objects  appear 
to  move  with  the  lenses  the  minus  is  too  strong, 
and  you  must  find  the  minus  lens  that  will 
allow  the  object  to  remain  stationary.  Whatever 
minus  lens  is  required  to  do  this  will  be  of  the 
same  power  as  your  plus  lens;  for  instance,  it 
will  require  a  —  3  sphere  to  neutralize  a  +  3 
sphere.  When  you  look  at  an  object  through 
a  minus  lens,  and  move  the  lens  as  explained 
above,  the  object  will  appear  to  move  with  the 
movement  of  your  lens,  and  in  order  to  find 
its  dioptric  power  use  plus  lenses  as  in  the 
previous  test  until  all  movement  of  the  object 
looked  at  has  disappeared,  and  then  the  minus 
lens  will  be  the  same  power  as  your  plus.  If 
the  lens  is  compound,  use  the  weakest  spherical 
lens  which  neutralizes  the  motion  in  one  direc- 
tion; this  usually  gives  the  spherical  surface, 
then  use  a  cylinder  to  neutralize  motion  at 
right  angles  to  this.  If  in  order  to  neutralize 
a  given  compound  lens,  +  2  sphere  combined 
with  -h  1  cylinder,  axis  90°  is  required,  then 
the  lens  being  neutralized  is  a  —  2  sphere  com- 
bined with  —  1  cylinder,  axis  90°,  etc. 

Nictitation     (nik-tit  a'-shun).       (L.    nictitare  =  to 


OPHTHALMIC  DICTIONARY  171 

wink.)     Involuntary  convulsive  twitching  of  the 
eyelids. 

Night  Blindness.     See  Nyctalopia. 

Niphablepsia  (nif-ab-lep'-si-ah).  (Gr.  nipha  = 
snow  +  ablepsia  ==  blindness.)  That  condition 
wherein  blindness  is  caused  by  the  glaring 
reflection  of  sunlight  upon  the  snow.  Snow- 
blindness. 

No'dal  Points,  or  Cardinal  Points.  Are  two  points 
situated  on  the  optic  axis,  connecting  the  cen- 
ters of  curvature  of  the  refracting  compound 
dioptric  system  of  the  eye.  The  nodal  points 
of  the  eye  are  so  close  together  that  they  may 
be  considered  as  one  point. 

Nodal  Points  of  a  Lens.  The  two  points  of 
the  principal  axis,  so  situated  that  every  ray 
which,  before  being  refracted,  is  directed  to- 
ward the  first  of  them,  seems,  after  its  refrac- 
tion, to  come  from  the  second  one,  and  takes  a 
direction  parallel  to  that  which  it  had  at  first. 
These  two  parallel  rays  are  called  lines  of 
direction,  and  act,  in  the  combined  system,  the 
same  part  as  the  line  passing  through  the 
nodal  point  of  a  single  refracting  surface. 

Normal.  (L.  norma  ^=  rule.)  That  which  con- 
forms to  the  natural  rule.  A  straight  line  drawn 
from  any  point  of  a  curve  or  surface  so  as  to 
be  perpendicular  to  the  curve  or  surface  at  the 
point  which  it  strikes  is  said  to  be  normal  to 
the  surface. 

Normal  Vision.  Vision  is  said  to  be  normal  when 
an  eye  can  read  a  line  on  Snellen's  Test  Type 
from  the  distance  at  which  it  is  numbered. 
The  smaller  the  objects  that  an  eye  can  dis- 


tinguish  or  the  greater  the  distance  at  which  it 
can  distinguish  an  object  of  given  size,  the 
greater  is  the  acuity  of  vision  that  it  possesses. 
Suppose,  for  instance,  that  the  eye  is  just  able 
to  distinguish  the  letters  in  the  line  marked  50 
on  the  Snellen's  test  type  from  a  distance  of 
twenty  feet,  then  the  vision  would  be  20/50. 
The  vision  in  this  case  would  not  be  as  good  as 
if  the  line  marked  40  had  been  read  from  the 
same  distance;  and  in  order  to  have  normal 
vision  the  patient  should  read  the  line  marked 
20  at  twenty  feet,  with  each  eye  separately, 
then  the  vision  would  be  known  as  20/20. 
Sometimes  the  patient  will  read  the  line 
marked  15  or  even  10  from  twenty  feet.  In 
this  case  the  vision  is  exceptionally  acute,  and 
is  designated  as  20/15  or  20/10. 

Normal  vision  does  not  indicate  that  the  eye 
is  normal,  as  the  patient  may  be  straining  to 
bring  the  vision  up  to  this  point,  as  in  Faculta- 
tive Hypermetropia.  Again,  an  emmetropic  eye 
does  not  always  have  normal  vision. 

Notation  (no-ta'-shun).  (L.  notare  =  to  mark.)  A 
system  of  written  signs  of  things  and  relations 
used  in  place  of  common  language. 

Nubecula  fnu-bek'-u-la).  (L.  dim  of  nubes  = 
cloud.)     Slight  cloudiness  of  the  cornea. 

Nuclear  fnu'-kle-ar).  Pertaining  to  the  center. 
The  controlling  center  of  activity. 

Nuclear  Cataract.    See  Cataract. 

Numeration.  (L.  numerare  =  to  count.)  The  art 
of  reading  numbers. 

Numerator    (nu'-me-ra-tor).      The    number,    in    a 


^OPHTHALMIC  DICTIONARY  173 

common  fraction,  which  shows  how  many  parts 
of  a  unit  are  taken. 

Nyctalopia  (nyk-tal-o'-pi-ah).  (Gr.  nycto  =  night 
-f-  alaos  =  obscure  -f  ops  =^  eye.)  Night  blind- 
ness. A  condition  where  a  person  does  not 
possess  normal  night  vision. 

Nyctotyphlosis  (nyk-to-tyf-lo'-sis.)  (Gr.  nyx  =  night 
+  typhlosis  ^-^  blindness.)  State  of  blindness 
at  night  time. 

Nystagmus  (nys-tag'-mus).  (Gr.  nystagmos  =  a 
nodding.)  Short,  jerking  movements  of  the  eye 
which  are  very  rapidly  repeated  and  always 
occur  in  the  same  direction.  The  movements 
of  the  eye,  as  a  whole,  are  not  affected  by  it. 
Defective  vision  of  such  cases  is  not  to  be  at- 
tributed to  the  nystagmus,  but,  on  the  con- 
trary, is  the  cause  of  it.  Vertical  n.,  the  eyes 
continually  move  vertically.  Lateral  n.,  the  eyes 
constantly  move  horizontally.  Rotary  n.,  the 
eyes  constantly  rotate. 


0 


BFUSCATIGN  (ob-fus-ka'-shun).  (L.  ob  =  to- 
ward +  fuscus  =  dark.)  An  obscuration  of  vision 
or  a  confusion  of  sight. 

Object.  Something  visible  or  tangible.  That 
which  is  seen.  An  external  something  the 
image  of  which  is  upon  the  retina,  which  is  in- 
telligently impressed  and  appreciated  by  the 
brain. 

Objective  (ob-jek'-tive).  (L.  ob  =^  against  4-Jacere 
-^  to  cast.)  Symptoms  observed  by  operator 
usually  with  ophthalmoscope  or  retinoscope. 
Symptoms  which  the  refractionist  discovers  by 


means  of  one  or  more  of  his  five  senses.  Ob- 
jective Examination.  An  examination  conducted 
independent  of  the  patient's  statements;  e.  g., 
retinoscopy,  ophthalmoscopy  and  many  other 
tests  by  means  of  instruments. 

Oblique.  Slanting;  placed  in  a  plane  between  the 
horizontal  and  vertical  planes. 

Occipital  (ok-sip'-it-al).  Pertaining  to  the  back 
part  of  head.  Occipital  lobe  is  the  posterior 
portion  of  the  cerebral  hemisphere. 

Occipito-Frontalis.      The    muscle   which    lifts    the 

eyebrows    upward.      Supplied    by    the    seventh 

nerve. 
Occlusion  of  the  Pupil   (ok-klew'-shun).     Blocking 

up  of  the  pupil  by  a  membrane. 
Ocellus  (o-sel'-lus).     (L.  "the  eye.")     A  single  aye. 
Ocular  (ok'-u-lar).   (L.  oculus  =  eye.)   That  which 

pertains  to  the  eye. 

Ocular  Refraction.  The  science  treating  of  the 
optical  conditions  of  the  eye,  the  estimation  of 
its  errors  of  refraction  and  their  connection 
with  lenses  for  the  eye. 

Ocular  Spectres.  Imaginary  objects  floating  be- 
fore the  eyes. 

Oculist  (ok'-u-list).  (L.  oculus  ^  eye.)  A  physi- 
cian and  surgeon  who  has  received  the  degree, 
"Doctor  of  Medicine,"  and  makes  a  specialty  of 
the  eye  and  its  diseases. 

Oculo-Motor  Center  is  a  point  situated  beneath 
the  floor  of  the  aqueduct  of  Silvius  around 
w^hich  the  impulse  to  u?8  accommodation  united 
with  the  action  to  use  the  different  muscles  of 
the  eye  is  stimulated. 


OPHTHALMIC  DICTIONARY  175 

Oculomotor  (ok'-yu-loh-moh'-tor).  (L.  oculus  = 
eye  +  motus  —  motion.)  Pertaining  to  the 
movements  of  the  eye. 

Oculus   (ok'-yii-his).     The  organ  of  vision. 

O.  D.    Oculus  Dexter.     The  right  eye. 

Offset  Guard.  An  eye-glass  guard  with  a  long 
shank,  the  purpose  of  which  is  to  hold  lenses 
farther  from  the  eyes. 

Old  Sight.     See  Presbyopia. 

O'nyx.  (Gr.  "nail.")  An  accumulation  of  pus  be- 
tween the  layers  of  the  cornea,  resembling  a 
finger  nail. 

Opacity  (o-pas'-i-ty).  (L.  opacus  =  obscure.)  The 
quality  of  that  which  is  opaque. 

Opaque  (o-pake').  Impervious  to  light.  Not  trans- 
parent. 

Operculum.  (L.  "lid,"  cover.)  Anything  resem- 
bling a  lid  or  cover. 

Operculum  Oculi  (o-per-cu'-lum  oc'-u-li).  The  eye- 
lid. 

Operation  (op-er-a'-shun).  (L.  opus  =  work.)  Ajj 
act  performed  with  instruments  or  by  the  hands 
of  a  surgeon. 

Ophryitis  (of-ry-i'-tis).  (Gr.  ophrys  =  eyebrow  + 
itis  =  inflammation.)  That  condition  in  which 
the  eyebrows  are  inflamed. 

Ophrys  fof'-rys).     (Gr.  eyebrow.) 

Ophthalmagra  (of-thal'-ma-grah).  (Gr.  ophthal- 
mos  eye  -}-  agra  ^  seizure.)  A  sudden  intense 
pain  in  the  eye.  usually  rheumatic  or  gouty  in 
origin. 


Ophthalmalgia  fof-thal-mar-ge-ah ).  (Gr.  ophthal- 
mos  =  eye  -j-  algos  ^  pain.)  Sudden  violent 
pain  in  the  eye,  not  the  result  of  inflammation, 
but  neuralgic  in  character. 

Ophthalmatrophia  (of-thal-mah-tro'-fe-ah).  (Gr. 
ophthalmos  =  eye  +  atrophia  =^  atrophy.)  Atro- 
phy of  the  eye. 

Ophthalmia  (of-thal'-mi-ah).  Severe  inflammation 
of  the  eye.  This  more  particularly  applies  to 
the  conjunctiva  of  the  eyelids  and  eyeball. 

OphthaI'mia  Neonato'rum.  (Gr.  ophthalmos  =■ 
eye  +  L.  neonatus  --=  new-born.)  A  form  of 
purulent  conjunctivitis  which  attacks  newly 
born  children. 

Ophthalmic    (of-thal'-mic).      That   which    pertains 

to    the    eye.      Ophthalmic    Lens,    a    lens    to    be 

worn  before  the  eye. 
Ophthalmitic   (of-thal-mit'-ic).  That  which  applies 

to  inflammatory  diseases  of  the  deeper  as  well 

as  the  superficial  structures  of  the  eye. 
Ophthalmitis  (of-thal-mi'-tis).     (Gr.  ophthalmos  = 

eye  +  itis.)       Inflammation    of    the    eye,    more 
•  especially  the  globe  with  its  membranes. 
Ophthalmoblennorrhoea     (blen-ur-ree'-ah).       (Gr. 

ophthalmos  =  eye  +  blenna  =^  mucus  +  rhoia  = 

flow.)     A  flow  of  mucus  from  the  eye. 
Ophthalmocarcinoma     (kahr-si-no'-mah).      Cancer 

of  the  eye. 
Ophthalmocele.      (Gr.  ophthalmos  ^  eye  -\-  kele  == 

hernia.)     See  Stapyloma.  '    - 

Ophthalmocopia    (koh'-pee-ah).      (Gr.   ophthalmos 

=  eye  +  kopos  =^  fatigue.)   Fatigue  of  the  eyes;  | 

Asthenopia. 


OPHTHALMIC  DICTIOXAIIV  177 

Ophthalmodynia    ( -iliir-e-ah  ).      (Gr.   ophthalmos 
eye  -r  odyne  -    pain.)       Neuralgic    pain    of    the 
eye. 

Ophthalmography  (mog'-rha-fee).  (Gr.  ophthal- 
mos eye ->- graphe  a  description.)  A  de- 
scription of  the  eye. 

Ophthalmologist  (of-thal-mol'-o-gist).  One  who 
practices  ophthalmology  and  has  taken  the  de- 
gree. "Doctor  of  Medicine."     An  Oculist. 

Ophthalmology  (of-thal-mol'-o-gy).  A  study  of  the 
eye  and  its  diseases. 

Ophthalmomacrosis    f-ma-kro'-sis).      Enlargement 

of  the   eyeballs. 

Ophthalmomalacia  (-ma-la'-sha).     (Gr.  ophthalmos 

—  eye  -+-  malakia  =  softness.)  That  condition 
in  which  there  is  abnormal  softness  of  the  eye- 
ball. 

Ophthalmopathy    (mop'-a-thee).      (Gr.  ophthalmos 

—  eye  +  pathos  ^  suffering.)  Any  disease  of 
the  eye. 

Ophthalmophthisis  (-mof'-thi-sis).  (Gr.  ophthal- 
mos eye  —  phthisis  wasting.)  That  condi- 
tion in  which  there  is  wasting  of  the  eyeballs. 

Ophthalmoplegia  (-ple'-je-ah).  (Gr.  ophthalmos — 
eye  f  plege  stroke.)  Paralysis  of  the  ocular 
muscles  of  the  eye.  O.  Partial,  a  form  in  which 
only  some  of  the  muscles  are  paralyzed.  O. 
Progressive,  a  gradual  paralysis  of  all  the  mus 
cles  ot  both  eyes.  O.  Total,  when  the  iris  and 
ciliary  body,  as  well  as  the  external  muscles, 
are  paralyzed.  O.  Externa,  when  the  external 
muscles  are  paralyzed.  O.  Interna,  paralvsis  of 
the  internal  muscles. 


Ophthalmoptoma    (-mop-to'-mah).      Protrusion    of 

the  eyeballs. 

Ophthalmoptosia  (-mop-to'-sia).  (Gr.  opht.halmos 
=  eye  +  ptosis  ^=  a  falling.)  Protrusion  of  the 
eyeball. 

Ophthalmorrhagia  (-mor-rha'-gee-ah).  (Gr.  oph- 
thalmos  =  eye  +  rhegnymi  =  I  burst  forth.) 
Hemorrhage  from  the  eye  or  orbit. 

Ophthalmorrhexis  (-mor-rex'-is).  (Gr.  ophthalmos' 
=  eye  +  rhexis  =  rupture.)  The  bursting  of 
the  eyeball. 

Ophthalmoscope  (of-thal '-mo-scope).  (Gr.  oph- 
thalmos =  eye  -j-  skopeo  =  I  examine.)  An  in- 
strument for  observing  the  interior  of  the  eye. 
and  thus  determining  the  appearance  of  the 
media,  the  condition  of  the  retina,  choroid  and 
optic  nerve,  and  the  state  of  the  refraction. 

The  Ophthalmoscope  consists  of  a  round 
mirror,  with  a  small  perforation  in  the  center. 
The  surface  of  the  mirror  is  usually  concave. 
The  more  improved  ophthalmoscopes  have  a 
reversible  mirror,  one  side  of  which  is  flat  and 
the  other  concave.  In  addition  to  this  there  are 
located  on  the  back  of  the  ophthalmoscope 
several  wheels  which  contain  a  great  variety  of 
convex  and  concave  lenses.  By  rotating  these 
wheels  the  different  lenses  contained  in  them 
can  be  thrown  immediately  behind  the  aper- 
ture in  the  mirror. 

There  are  two  methods  of  examining  the  eyes 
with  the  ophthalmoscope,  viz.:  the  indirect  and 
the  direct. 

The  indirect  method  is  not  of  much  value  so 
far  as  estimating  the  refraction  of  the  eye  is 


^ 


OPHTHALMIC  DICTIONARY 


1T9 


concerned,  but  gives  a  good  view  of  the  fundus 
of  the  eye.  enabling  us  to  examine  in  minute 
detail  the  optic  disc  and  the  blood  vessels  of 
the  retina ;  also  to  observe  whether  any  dis- 
eased condition  exists  in  the  interior  of  the 
eyeball. 

To  perform  this  method  successfully,  we  seat 
our  patient  in  the  dark  room  and  place  a  light, 
either  an  argand  gas  burner,  an  electric  light, 
or  any  ordinary  kerosene  student's  lamp,  at  the 
side  and  slightly  back  of  the  patient's  head.  If 
we  wish  to  examine  the  left  eye  we  place  the 
light  on  the  left  side  of  the  patient's  head,  and 
if  we  wish  to  examine  the  right  eye,  on  the 
right  side.  We  place  the  light  just  far  enough 
back  of  the  head  to  avoid  illuminating  the  pa- 
tient's face.     We  take  our  seat  in  front  of  the 


patient  and  hold  our  ophthalmoscope  at  the 
focal  distance  of  its  mirror,  reflect  the  light 
into  the  patient's  eye,  and  look  through  the 
sight  hole  in  our  mirror.  The  next  step  is  to 
place  a  strong  convex  lens  immediately  in 
front  of  our  patient's  eye.  With  our  mirror  we 
illuminate  the  retina,  and  the  rays  emanating 


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well  to  place  the  patient  under  the  influence 
of  atropine,  assuming  that  the  operator  haj^ 
thorough  control  of  his  own  accommodatiou 
and  can  suspend  it  at  will. 

By  reflecting  the  light  into  the  Emmetropic 
eye  we  Illuminate  the  retina;  the  retina  again 
reflects  the  light  so  that  it  passes  through  the 
pupil  and  out  of  the  eye.  The  rays  from  eacli 
reflecting  point  emerge  from  the  eye  as  parallel 
rays.  Therefore,  if  the  operator's  eye  is  Emme- 
tropic he  will,  by  the  aid  of  these  rays,  be  able  to 
distinctly  see  the  details  of  the  fundus  in  the 
back  part  of  his  patient's  eye,  because  the 
light  leaves  the  patient's  eye  as  parallel  rays, 
and  the  operator's  eye,  being  also  emmetropic, 
is  adapted  for  parallel  rays,  and  hence  he  has 
each  point  on  the  patient's  retina  represented 
by  an  exact  focus  on  his  own  retina. 

It  can  readily  be  seen  that  if  a  patient  has 
used  any  accommodation  the  rays  would  leave 
his  eye,  not  as  .parallel,  but  as  convergent  rays, 
and  therefore  the  operator  would  have  been 
unable  to  distinctly  see  the  details  of  the  fun- 
dus. On  the  other  hand,  if  the  patient  had  been 
under  the  influence  of  atropine  and  the  rays 
had  left  the  eye  as  parallel  rays  striking  the 
observer's  emmetropic  eye,  as  parallel  rays, 
they  would  not  focus  upon  the  operator's  retina 
if  he  had  used  any  accommodation.  Hence  the 
necessity  of  thorough  relaxation  of  accommo- 
dation in  both  the  patient  and  operator. 

We  will  next  suppose  that  the  hypermetropic 
eye  is  being  examined  by  an  operator  who  is 
emmetropic.  The  rays  of  light  will  leave  the 
hypermetropic  eye  as  divergent  rays  and  there- 


OPHTHALMIC  DICTIONARY 


18[ 


fore  will  not  focus  upon  the  retina  of  the  ob- 
server's emmetropic  eye,  and  hence  he  will  be 
unable  to  distinctly  see  the  details  of  the  fun- 
dus in  the  patient's  eye.  He  now  rotates  the 
wheel  on  the  back  of  his  ophthalmoscope, 
throwing  different  lenses  into  the  aperture  of 
the  mirror,  until  finally  he  strikes  one  which 
enables  him  to  distinctly  see  his  patient's 
retina.  The  glass  which  produces  this  result 
will    represent    the    measure    of    his    patient's 


hypermetropia.  In  order  that  the  operator  may 
distinctly  see  the  patient's  retina,  he  must  use 
a  convex  glass  strong  enough  to  render  parallel 
the  divergent  rays  which  are  leaving  his  pa- 
tient's eye. 

In  myopia  the  patient's  eye  is  too  long,  and 
the  rays  of  light  which  leave  the  myopic  eye 
will  therefore  leave  as  convergent  rays  and 
focus  in  front  of  the  observer's  retina,  so  that 
in  this  case  he  will  also  be  unable  to  distinctly 
see  the  fundus  of  his  patient's  eye,  and  as  in 
the  case  of  the  hypermetropic  eye  he  rotates 
the  wheel  on  his  ophthalmoscope  until  he  is 
able  to  distinctly  see  the  retina  of  the  myopic 
eye.  The  glass  which  accomplishes  this  result 
is  the  measure  of  the  patient's  myopia. 

In  order  that  he  may  distinctly  see  the  back 


of  this  eye,  a  concave  glass  must  be  used  strong 
enough  to  render  parallel  the  convergent  rays 
which  are  leaving  the  myopic  eye. 

It  is  usually  conceded  that  in  astigmatism 
the  ophthalmoscope  is  of  little  or  no  value.  It 
is  true  that  we  may  be  able  to  see  the  blood- 
vessels and  the  edges  of  the  optic  disc  clearer 
in  one  meridian  than  in  another,  and  that  we 
may  use  a  glass  strong  enough  to  render  plain  the 


meridian  which  was  at  first  blurred,  and  there- 
by dim  the  meridian  which  was  first  seen 
plainly.  The  glass  which  clears  up  the  merid- 
ian which  seemed  blurred  at  first  would  be  the 
measure  of  the  ametropia  in  the  meridian  at 
right  angles  to  it. 

It  must  also  be  remembered  that  if  the  operator 
is  not  emmetropic  he  must  either  have  his  own 
refraction  properly  corrected  by  glasses,  or  he 
must  make  deductions  or  additions,  as  the  case 
may  be,  to  or  from  whatever  glass  clears  up  the 
retina  in  the  patient's  eye.  For  instance,  if 
the  operator  knows  himself  to  be  hypermetropic 
to  the  extent  of  one  dioptry.  and  on  examining 
his  patient's  eye  he  finds  that  a  plus  3-D.  glass 
is  required  to  enable  him  to  see  the  details  of 
his  patient's  fundus,  he  then  knows  that  his 
patient  has  two  dioptries  of  hypermetropia,  "be- 


OPHTHALMIC  DICTIONARY  185 

cause  one  of  the  three  was  required  to  correct 
his  own  eye.  and  likewise  if  he  had  been  exam 
ining  a  myopic  eye  and  found  that  a  minus  2-D. 
lens  was  required  to  see  his  patient's  retina,  he 
would  know  that  his  patient  had  three  dioptries 
of  myopia,  because  he  himself  was  one  dioptry 
hypermetropic. 

Ophthalmoscopy  (oph'-thal-mos'-copy).  The  art  of 
judging  healthy  or  diseased  conditions  of  the 
eyes  by  means  of  the  ophthalmoscope.  There 
are  two  methods  of  examining  the  eyes  with 
the  ophthalmoscope,  viz.:  the  direct  and  the 
indirect. 

Ophthalmostat  (of-thal'-mo-stat).  (Gr.  ophthal- 
mos  =^  eye  +  statos  =^  made  to  stand.)  An  eye- 
speculum. 

Ophthalmula  (of-thal'-mu-lah).  A  cicatrix  located 
upon  the  eye  or  its  appendages. 

Optic.  (Gr.  opsis  =  vision.)  That  which  pertains 
to  the  science  of  light,  and  also  to  the  eye 
itself,  together  with  its  functions. 

Optic   Atrophy.     A   partial   or  total  loss   of  sight 

due  to  atrophy  of  the  optic  nerve. 
Optic  Axis.     A  line  drawn  through  the  center  of 

the    cornea,    through    the    nodal    point    to    the 

inner  side  of  the  macula  lutea.    In  other  words, 

through  the  center  of  the  eyeball  from  before 

back. 
Optic  Groove.     A  transverse  groove  on  the  upper 

surface  of  the  sphenoid  bone  on  which  the  optic 

nerve  rests. 
Optic  Nueritis.     Inflammation  of  the  optic  nerve. 
Optical.    Pertaining  to  the  organ  of  vision. 


optical  Center.  A  point  where  the  secondary 
axis  crosses  the  principal  axis  on  line  with  the 
thickest  part  of  a  plus  sphere  or  the  thinnest 
part  of  a  minus.  A  ray  of  light  when  passing 
through  the  optical  center  of  a  lens  will  always 
emerge  parallel  to  the  incident  ray  or  in  the 
same  plane.  Optical  Center  of  a  Lens.  The 
center  of  refraction.  It  is  found  by  making  two 
parallel  radii  of  curvature,  and  connecting  the 
points  in  which  they  meet  the  surfaces.  The 
point  at  which  this  line  cuts  the  principal  axis, 
is  the  optical  center. 

Optical  Corrections.  Lenses  that  change  the  di- 
rection of  light  rays  entering  the  eyes  to  such 
an  extent  that  the  eyes  are  adapted  to  receive 
and  focus  them  upon  the  retina,  creating  artifi- 
cial emmetropic  conditions  when  ametropic  con- 
ditions exist. 

Optic  Commissure  (kom'-mis-ur).  The  linking  or 
joining  together  of  the  right  and  left  optic 
nerve. 

Optic  Disc.  That  spot  on  the  retina  which  marks 
the  entrance  of  the  optic  nerves  into  the  eye. 
It  is  also  called  the  blind  spot,  or  papilla. 

Optic  Excavation.  The  depression  in  the  optic 
disc. 

Optic  Nerve.    See  under  nerve. 

Optic  Papilla  (pap-il'-lah).  The  elevation  of  the 
optic-nerve  head;  also  called  the  optic  disc  and 
blind  spot. 

Optician  (op-tish'-an).  A  person  skilled  in  tlie 
manufacture  of  optical  instruments. 


OPHTHALMIC  DICTIONARY  187 

Optics.  That  part  of  the  science  of  physics  which 
deals  with  the  transmission  of  liglit,  the  laws 
of  refraction,  reflection  and  the  phenomena  of 

vision. 

Optic  Tract.  The  optic  nerve  between  the  visnal 
centers  and  the  optic  commissure. 

The  Optic  Nerve,  which,  in  part,  is  known  as 
the  optic  tract,  is  formed  by  two  roots,  in  ihe 
floor  of  the  brain,  the  external  and  the  internal 
roots. 

The  External  Root  has  its  origin  in  three  gray 
matter  centers:  (1)  The  optic  thalamus;  (2) 
the  external  geniculate  (knee-like)  body,  and  the 
anterior  tubercles  of  the  corpora  quandrige- 
mina   (four  bodies). 

The  Internal  Root  arises  from  two  gray  mat- 
ter centers;  they  are  the  internal  geniculate 
body  and  the  posterior  tubercles  of  the  corpora 
quadrigemina   (four  bodies). 

These  sight  centers  which  give  origin  to  the 
optic  tracts  are  connected  to  the  cerebral  cor- 
tex by  a  number  of  fibers  known  as  the  cor- 
tico  optic  radiating  fasciculi  and  form  the  most 
posterior  part  of  the  optic  thalamus  (bedj. 
These  later  fibers  are  supposed  to  be  of  a  sen- 
sory nature,  and  to  communicate  with  the  dif- 
ferent sections  of  the  brain.  The  fibers  of  the 
external  and  internal  roots  come  together  to  form 
the  optic  tract,  it  passes  forward  along  under 
the  posterior  of  the  optic  thalamus,  crosses  the 
crus  cerebri,  and  again  crosses  the  side  of  the 
tuber  cinerium  to  the  optic  groove  on  the 
sphenoid  bone  where  it  unites  with  the  optic 
tract  of  the  other  side  to  form  the  optic  com- 
missure.    In  the  optic  commissure  the  fibers  of 


each  optic  tract  divide,  and  the  outer  fibers  of 
each  tract  are  continued  into  the  nerve  of  the 
same  side,  while  the  central  fibers  of  each  tract 
continue  into  the  optic  nerve  of  the  opposite 
side,  crossing  each  other  and  passing  througli 
the  optic  foramen  to  enter  the  eye. 

The  dura  mater  and  pia  mater  which  lines 
the  skull  passes  through  the  optic  foramen 
(hole  into  orbit)  and  forms  the  optic  sheath  or 
covering  of  the  optic  nerve  until  it  enters  the 
lamina  cribrosa  (sieve-like  opening  of  the  eye) 
and  spreads  out  to  form  the  retina. 

Optist   (op'-tist).     A  person  skilled  in  optometry. 

Optogram  (op'-to-gram).  (Gr.  optos  =  visible + 
gramma  =  a  picture.)  A  faint  image  stamped 
on  the  retina  for  a  brief  period. 

Optology  (op'-tol-o-ge).     See  Optometry. 

Optometrist.  One  who  measures  the  eye's  refrac- 
tion. 

Optometry  (op-tom'-e-try).  (Gr.  optikos  =  be- 
longing to  sight  -f  metron  =^  measure.)  The 
science  and  art  of  employing  the  various  meth- 
ods of  measuring  the  optical  state  of  the  eye. 

O'ra  Serra'ta  (a  serrated  border).  The  anterior 
limit  or  edge  of  the  retina.  So  named  from  its 
saw-like  appearance. 

Orb.    A  spherical  body. 

Orbicular.  (L.  orbiculus  =  a  small  disc.)  Annu- 
lar, circular. 

Orbicularis  Palpebrarum.  The  circular  muscle  of 
the  eyelids. 

Orbiculus  Ciliaris.     A  zone  of  about  one-sixth  of 


OPHTHALMIC  DICTIONARY  ISft 

an  in^n  in  width.     It  is  directly  continuous  with 
the  anterior  part  of  the  choroid. 

Orbit  (or'-bit).  (L.  orbita  =  track).  The  bony 
socket  in  which  the  eyeball  is  placed.  The 
orbits  are  conical  in  shape  with  their  apices 
extending  backward  and  toward  each  other 
while  the  front  or  base  of  the  cone  is  open, 
leaving  the  eyeballs  to  be  protected  by  the  eye- 
lids in  front. 

Anatomy  of  Orbits.  The  orbits  are  two  pyra- 
midal cavities  1%  inches  wide  by  1%  inches 
deep,  situated  at  the  upper  and  anterior  part 
of  the  face,  their  bases  being  directly  forward 
and  outward  and  their  apices  backward  and 
inward,  so  that  the  axes  of  the  two  if  continued 
backward  Avould  meet  over  the  body  of  the 
sphenoid  bone.  The  orbit  is  lined  with  perios- 
teum, the  periorbita.  Each  orbit  is  formed  of 
seven  bones,  the  frontal,  the  sphenoid,  ethmoid, 
superior  maxillary,  malar,  lachrymal  and  pal- 
ate; but  three  of  these,  the  frontal,  ethmoid  and 
sphenoid,  enter  into  the  formation  of  both  or- 
bits, so  that  the  two  cavities  are  formed  of 
eleven  bones  only.  The  orbital  opening,  or 
mouth,  is  called  aditus  orbitae  (Aditus  Orbitae 
— entrance  to  orbit).  At  the  apex,  or  back  part 
of  the  orbit  on  the  nasal  side,  is  a  small  circu- 
lar opening  known  as  the  optic  foramen,  which 
transmits  the  optic  nerve  and  ophthalmic 
artery.  There  are  nine  openings  communi- 
cating with  each  orbit,  viz.,  the  optic  foramen, 
the  spheno-maxillary  fissure,  sphenoidal  fissure, 
supraorbital    foramen,    anterior    and    posterior 

•  ethmoidal  foramina,  infraorbital  canal,  malai 
foramina,    and    the    canal    for    the    nasal    duct. 


Sphenomaxillary  fissure  transmits  the  superior 
maxillary  nerve  and  its  orbital  branches,  the 
mfraorbital  vessels,  and  the  ascending  branches  - 
from  the  spheno-palatine  or  Meckel's  ganglion. 
Sphenoidal  fissure  transmits  the  third,  the 
fourth,  the  three  branches  of  the  ophthalmic 
division  of  the  fifth,  the  sixth  nerve,  some  fila- 
ments from  the  cavernous  plexus  of  the  sympa- 
thetic, the  orbital  branch  of  the  middle  menin- 
geal artery,  and  a  branch  from  the  lachrymal 
artery  of  the  dura  mater,  and  the  ophthalmic 
vein.  Supraorbital  foramen  transmits  the 
supraorbital  artery,  nerve  and  vein.  Anterior 
ethmoidal  foramen  transmits  the  anterior  eth- 
moidal vessels  and  nasal  nerve.  Posterior  eth- 
moidal foramen  transmits  the  posterior  eth- 
moidal vessels.  Infraorbital  canal  opens  just 
below  the  margin  of  the  orbit.  Malar  foramina 
is  a  passage  for  nerves  and  vessels  from  the 
orbit. 

Orbital  (or'-bit-al).    Pertaining  to  the  orbit. 

Origin  (or'-ij-in).  (L.  origo  =  beginning.)  The 
more  fixed  end  of  a  muscle;  for  instance,  the 
end  attached  to  the  bone  of  the  orbit. 

Orthochromatic  (or-tho-chro-mat'-ic).  (Gr.  orthos 
=  straight -|- chroma  =  color.)  A  term  used 
by  photographers  denoting  that  the  colors  are 
normal  or  correct. 

Orthometer  (or-thom'-e-ter).  (Gr.  orthos  =  straight 
-f-  metron  =  measure.)  An  instrument  for  find- 
ing the  exact  relative  protrusion  of  the  two  eye- 
balls. 

Orthoptic  (or-thop'-tic) .  (Gr.  orthos  =  straight -f 
optikos  =  relating  to   sight.)      Relating  to    the 


OPHTHALMIC  DICTIONARY  191 

straightening  of  a  deviating  eye  by  means  of 
exercise. 

Orthophoria  (or-tho-foh'-ree-ah).  (Gr.  orthos  = 
straight  +  phoria  =  tending.)  That  condition 
in  which  the  eyes,  or  better,  the  visual  axes,  are 
parallel  when  the  extrinsic  muscles  are  in  a 
state  of  rest.    Perfect  muscular  balance. 

Orthoptic  (or-thop'-tic).  (Gr.  orthos  =  straight -f 
optikos  ^  relating  to  sight.)  Correcting  hetero- 
phoria,  or  strabismus,  by  means  of  the  prism 
exercise.  This  is  accomplished  by  placing  the 
base  of  the  prism  over  the  strong  muscle,  thus 
causing  the  weak  muscle  to  contract  or  draw 
the  eye  toward  the  apex  of  the  prism  in  order 
to  see. 

Orthoscope  (or'-tho-scoI)e).  (Gr.  orthos  =  straight 
-f  skopeo  =-  I  view.)  An  instrument  for  neu- 
tralizing the  refraction  of  the  cornea  by  exam- 
ining it  through  water. 

Orthoscopic  Lenses.  A  lens  with  two  elements — 
a  sphere  and  a  prism — so  arranged  that  the 
amount  of  accommodation  and  convergence 
used  should  exactly  correspond. 

Orthotropia      (or-tho-tro'-piah).       (Gr.     orthos  = 

straight  +  trope  =—  turn.)        Perfect      binocular 

V      fixation.    With  this  condition  heterophoria  may 

I    exist  and   some  muscle  or  muscles  are   under 
strain  to  hold  the  eyes  parallel,  yet  it  is  gen- 
erally accompanied  by  orthophoria. 
Osseous  (os'-e-us).    Bony.    Resembling  bone. 
O.  S.  (Oculus  Sinister).    Left  eye. 
O.  U.  (Ovular  Unati).    Both  eyes. 


Oxyopia  (ox -y-o'-pi-ah).  (Gr.  oxys  =  acute  +  ops 
=  eye.)  That  condition  in  which  the  sight  is 
abnormally  acute. 


1  ACHYBLEPHARON  (pach-y-blef-ar'-on).  (Gr. 
pachys  =  thick  +  blepharon  =  eyelid.)  That 
condition  in  which  the  eyelids  have  become 
thickened. 

Palpebra  (pal'-pe-brah).  (L.  palpetare  =  to  palpi- 
tate.) The  eyelid.  Inferior  P.,  lower  eyelid. 
Superior  P.,  upper  eyelid.  Tertia  P.,  third  eye- 
lid.   See  Membrana  Nictitians. 

Palpebral  (pal'-pe-bral).  (Gr.  palpebra  =  eyelid.) 
That  which  relates  to  the  eyelid. 

Palpebral  Fissure  fpal'-pe-bral).  The  space  be- 
tween the  free  margins  of  the  eyelids.  The 
outer  angle  of  fissure  is  called  the  external  can- 
thus;  the  inner  angle,  the  internal  canthus. 
The  small-  space  between  the  lids  and  globe  at 
inner  angle  is  called  the  lacus  lachrymalis. 

Palpebrltis  (pal-pe-bri'-tis).  (L.  palpebra  =  eyelid 
4-  Gr.  itis  =  inflammation.)  An  inflammation  of 
the  eyelids. 

Pannus  (pan'-nus).  (L.  "a  piece  of  cloth.")  A 
web-like  patch  of  grayish  membranish  tissue 
usually  covering  the  upper  half  of  the  cornea, 
making  it  almost  opaque.  It  is  usuallv  caused 
by  the  rubbing  of  roughened  or  granulated  lids 
over  the  cornea  and  results  in  the  eifort  of 
nature  to  protect  this  membrane. 

Panophthalmia  (pan-of-thal'-mi-ah).  An  inflamma- 
tion of  the  entire  eye  structure. 


OPHTHALMIC  DICTIONARY  193 

Panophthalmitis  ( pan-off -thal-mi'-tis).  (Gr.  pas 
(pan)  =  all  +  ophthalmos  =  eye.)  General  in- 
flammation of  the  eyeball. 

Pantiscopic.     A  lens  tilted  outward  at  the  top. 

Pantometer  (pan-tom'-e-ter).  An  instrument  for 
measuring  angles  and  determining  perpendicu- 
lars. 

Papilla  (pap-il'-lah).  (L.  "nipple.")  A  conic  ele- 
vation observable  at  the  optic-nerve  head.  P. 
Lachrymal  is,  the  mound  at  the  inner  canthus 
of  the  eye  pierced  by  the  lachrymal  puncta. 

Papillitis  (pap-il-li'-tis).  That  condition  in  which 
tliere  is  an  inflammation  of  the  optic  disc  or 
papilla. 

Papilloretinitis  (pap-il-lo-ret-in-i'-tis).  Inflamma- 
tion of  the  optic  disc  and  retina. 

Parablepsis  (par-ab-lep'-sis).  (Gr.  para  ^  beside 
+  blepsis  =  sight.)     False  vision, 

Paracente'sis.  (Gr.  para  =  beside  -f  kentesis  = 
puncture.)     Surgical  puncture  of  a  cavity. 

Paracentesis  Cornea  (-sen-tee'-sis).  Puncture  of 
the  cornea. 

Parallax  (par'-al-lax).  An  apparent  displacement 
of  an  object,  due  to  change  in  the  observer's 
position,  or  when  closing  one  eye. 

Parallel    (par'-al-lel).      That    which    pursues    the 

same  direction,  but  in  a  separate  path. 
Parallelepiped     (par-a-lel-e-pip'-ed).       (Gr.     paral- 

lelos  =  parallel  +  epipedon  =  plane.)      A   prism 

whose  bases  are  parallelograms. 
Parallelogram    (par-a-lel'-o-gram).     (Gr.  parallelos 

=—  parallel  +  gramma  =  line.)      A    quadrilateral 

whose  opposite  sides  are  parallel. 


Parallelism  (par'-al-lel-ism).  State  of  being  par- 
allel. That  condition  in  which  the  visual  axes 
of  both  eyes  lie  in  nearly  parallel  paths. 

Paral'ysis.  (Gr.  "I  loosen" — "I  relax.")  That  con- 
dition in  which  there  is  a  loss  of  power  of  vol- 
untary motion  or  of  sensation  in  a  part  from 
lesion  of  nerve  substance.  Oculo-motor  P., 
where  the  motor  oculi  nerve  is  affected. 

Paralysis  of  Accommodation.  That  condition  in 
which  the  function  of  the  branch  of  the  third 
nerve  which  supplies  the  ciliary  muscles  has 
been  interrupted  and  the  eye  cannot  accommo- 
date, the  ciliary  muscles  being  in  a  state  of  rest. 

Paralyt'ic.  (Gr.  affection.)  Pertaining  to,  or 
affected  with,  paralysis;  a  person  who  is 
affected  with  paralysis. 

Paresis  (par'-es-is).  (Gr.  "a  relaxing.'")  A  slight 
form  of  paralysis. 

Paropsis  (par-op'-sis).  (Gr.  para  ^  beside -^opsis 
=  vision.)  That  condition  in  which  the  vision 
is  disordered,  and  may  be  due  to  either  a  false 
impression  being  made  upon  the  retina  or  a  dis- 
ordered condition  of  the  mind. 

Passive.  (L.  passivus  =  to  endure.)  That  which 
is  not  active;  for  instance,  a  muscle  that  is  in  a 
state  of  rest. 

Pathetic  (pa-thet'-ik).  That  which  pertains  to 
the  feelings.  The  pathetic  muscle  is  the  su- 
perior oblique  muscle  of  the  eye,  which  receives 
its  name  from  the  fact  that  the  patheticus.  or 
fourth  pair  of  cranial  nerves,  control  its  move- 
ments. 

Pathologic.    Pertaining  to  diseased  conditions. 


OPHTHALMIC  DICTIONARY  105 

Pathological    (path-o-log'-i-cal).     See  Pathology. 

Pathology  fpath-or-o-je).  (Gr.  pathos  =  suffering 
-f  logis  discourse.)  The  science  which  has  for 
its  object  the  knowledge  of  disease. 

Pediculis  Pubis  (ped-ik'-u-lus  pu'-bis).  (L.  "crab- 
louse.")  Crab-louse.  In  very  rare  cases  they 
will  reach  the  eyelashes  and  flourish  there.  The 
lice  cling  close  to  the  border  of  the  lid,  and 
look  like  dirty  scabs;  the  eggs  are  darker,  and 
may  also  be  mistaken  for  bits  of  dirt.  The  ab- 
sence of  inflammation  and  the  rather  peculiar 
appearance  will  lead,  in  doubtful  cases,  to  the 
use  of  a  magnifying  glass,  by  which  the  ques- 
tion will  be  settled  at  once. 

Penumbra  (pe-num'-brah).    A  partial  shadow. 

Perception.  (L.  percipere  =  to  perceive.)  The 
acquiring  of  impression  through  the  senses. 
Centers  of  sight  p.,  those  portions  of  the  brain 
that  are  the  sources  of  the  optic  nerves. 

Perceptivity  (per-sep-tiv'-it-e).  Capacity  to  re- 
ceive impressions. 

Perfection  Bifocal.     See  Bifocal. 

Perichoroidal  (-koh-roy'-dul).  That  which  sur- 
rounds the  choroid   membrane. 

Pericorneal  f  per-i-cor'-ne-al).  (Gr.  peri  =  around.) 
That  which  is  situated  around  the  cornea. 

Perimeter  (per-im'-e-tur).  (Gr.  peri  =^  around -f- 
metron  ~-=  measure.)  An  instrument  for  meas- 
uring the  field  of  vision. 

Perimetry  fpe-rim'-et-re).  (Gr.  perimetros  =  cir- 
cumference.)    Measurement  of  the  visual  field. 

Periocular  fper-e-ok'-u-lar).  (Gr.  peri  =  around -f 
L.  oculus  -    eye.)  That  which  encircles  the  eye. 


Perioptic.     See  Periocular. 

Perioptometry  (per-e-op-tom'-et-re).  (Gr.  peri  = 
around  +  optikos  =  referring  to  vision  —  metron 
=  measure.)  Measurement  of  the  visual  acuity 
of  the  retinal  periphery. 

Periorbita  rper-i-or'-bit-a).  (Gr.  peri  =  around  + 
L.  orbita  =  orbit.)  That  which  relates  to  the 
lining  membrane  of  the  orbit. 

Periorbital  (per-i-or'-bit-al).  Around  or  about  the 
orbit. 

Periorbitis  (per-e-or'-bi-tis).  Inflammation  of  the 
lining  membrane  of  the  bones  of  the  orbit. 
Orbital  periostitis.  ^ 

Periosteitis  (per-e-os-te-i'-tis).  Inflammation  of 
the  periosteum. 

Periosteum  (per-e-os'-te-um).  (Gr.  peri-=^  around 
-f  osteon  =bone.)  The  tough,  fibrous  mem- 
brane investing  a  bone. 

Peripheraphose  fper-if-er'-af-oz).  The  subjective 
sensation  of  a  dark  spot  in  a  patch  of  light,  the 
cause  residing  in  the  eye,  optic  nerve  or  out- 
side of  optic  center  in  the  brain. 

Periphacitis  Tper-i-fa-si'-tis).  CGr.  peri  =  around 
+  phakos  =  lens  —  itis.)  Inflammation  of  the 
crystalline  lens  of  the  eye.  _ 

Periphacus  (per-if-a'-cus).  The  crystalline  lens 
capsule. 

Periphery  (per-if'-er-y).  (Gr.  peri —around -r 
phero  =  I  carry.)  Any  outward  part  or  sur- 
face; for  instance,  the  border  of  the  cornea  or 
crystalline  lens. 

Periscopic  (per-is-cop'-ic).  (Gr.  peri  =  around -}- 
skopeo  =  I    view.)      A   lens    having    a    concave 


OPHTHALMIC  DICTIONARY  197 

and  convex  surface.  Periscopic  lenses  are  also 
called  meniscus  lenses;  taken  from  a  Greek 
word  meaning  a  crescent.     See  Lens. 

Peritomy  (per-it'-o-me).  (Gr.  peri  =  around  + 
tome  =  incision.)  An  operation  for  the  treat- 
ment of  pannus,  by  removing  a  strip  of  the  con- 
junctiva around  the  cornea. 

Perivascular  (per-i-vas'-ku-lar).  (Gr.  peri  =  around 
+  L.  vasculum  =  vessel.)   Surrounding  a  vessel. 

Perivascuirtis.  (Gr.  peri  =  around  +  L-  vasculum 
=  vessel  +  itis.)  Inflammation  of  the  sheath 
of  a  vessel.  This  is  an  increase  or  a  hyperplasia 
of  the  connective  tissue  about  the  vessels,  prin- 
cipally, and  usually,  the  arteries. 

Perspicilium  (per-spic-il'-i-um).  An  apparatus  to 
enable  an  individual  to  see  minute  bodies,  or 
which  will  improve  the  eyesight. 

Pescorvi'nus.  That  which  is  commonly  knov^nas 
crow's  foot;  or  wrinkles  at  the  outer  corner  of 
the  eye. 

Petit.  Frangois  Pourfour  du  Petit,  French  sur- 
geon and  anatomist,  1664-1741. 

Petit's  Canal.  The  space  between  the  suspensory 
ligaments  in  which  the  edge  of  the  crystalline 
lens  with  its  capsule  is  inserted. 

Phaco  (fak'-o).  Prefix  meaning  of,  or  pertaining 
to,  a  lens,  especially  the  crystalline  lens. 

Phacitis  (fas-i'-tis).  (Gr.  phakos  =  lens -f  Itis.) 
Inflammation  of  the  crystalline  lens. 

Phacomalacia  (fak-o-mal-a'-she-ah).  (Gr.  phakos 
=  lens  +  malakia  =  softness.)     A  soft  cataract. 

Phacometer  (fa-com'-e-ter).  (Gr.  phakos  =^  lens -f 
metron  =  measure.)     An  instrument  for  meas- 


iiring  the  curvature  of  lenses,  and  so  determin- 
ing their  refractive  power;  if  they  are  cylin- 
drical, will  locate  their  axes. 

Phacosclerosis  (fa-ko-scle-ro'-sis).  (Gr.  phakos  = 
lens  +  sklerosis  -^  hardening.)  Hardening  of 
the  crystalline  lens. 

Phacoscope  (fa'-ko-scope).  (Gr.  phakos  =  lens + 
skopeo  ^=  1  view.)  An  instrument  used  for 
viewing  the  accommodative  changes  of  the 
crystalline  lens. 

Phakitis  (fa-ki'-tis).  (Gr.  phakos  —  lens  +  itis.) 
Inflammation  of  the  lens,  A  supposition  exists 
that  the  crystalline  lens  may  become  inflamed. 

Phantasma  (fan'-tas-mah).  (Gr.  phantasma  ^  an 
appearance.)  A  disease  of  the  eye  in  which 
imaginary  objects  are  seen. 

Phengophobia  (fen-go-fo'-bi-ah).  (Gr.  piiengos  = 
daylight  -f  phobos  =  fear.)      See    Photophobia. 

Phimosis   (fi-mo'-sis)   Constriction.     (Gr.  "to  muz- 
zle.")    Abnormal  smallness  (as  of  the  palpebral 
fissure). 

Pho'rotone.  (Gr.  phora  =  motion  +  tonos  ten- 
sion.) An  instrument  for  exercising  the  mus- 
cles of  the  eye. 

Phosgenic      (fos-jen'-ik).        (Gr.      phos  ^  light  + 
gennao  =^--  to  produce.)     Light  producing. 

Phlyctenula  (flik-ten'-u-lah).  ((!r.  "blister.")  A 
small  vesicle  or  blister. 

Phlysis   (fly'-sis).     A  corneal  ulcer. 
Phoria.     (Gr.  "a  tending.") 

Phonometer.  An  instrument  for  determining  the 
insufliciencies  of  the  external  ocular  muscles. 


r 


OPHTHALMIC  DICTIOXART  1»{> 

Phorometroscope  (phor-o-met'-ro-scope).  An  in- 
strument for  determining  the  amount,  correc- 
tion and  treatment  of  muscular  asthenopia  by 
gymnastic  exercise  of  the  extrinsic  muscles. 

Phoroscope.  An  instrument  in  the  form  of  a  head- 
rest, with  a  clamp  attached  so  that  it  may  be 
fastened  to  a  table,  and  is  used  as  a  fixed  trial 
frame. 

Phose  (foz).  (Gr.  phos  =  light.)  A  subjective 
sensation  of  light  or  color. 

Phosphenes  (fos'-feenz).  (Gr.  phos  =  light -f- 
phaino  =^  I  show.)  A  luminous  sensation  caused 
by  pressing  on  the  eyeball. 

Phosphorescence  ffos-fo-res'-ens),  (Gr.  phos  =: 
light  -r  phoros  =  bearer.)  The  quality  of  be- 
coming luminous  in  the  dark  without  sensible 
heat. 

Photalgia  rto-tal'-je-ah).  (Gr.  phos  =  light -f- 
algos  =  pain.)  Pain  in  the  eye  arising  from 
too  much  light. 

Photochromatic  (fo-to-chro-mat'-ic).  TGr.  phos  = 
light  4-  chroma  =  color.)  That  which  pertains 
to  various  colored  lights. 

Photodysphoria.     See  photophobia. 

Photogenic.     See  Phosgenic. 

Photology  ffo-tol'-o-gy).    The  science  of  light. 

Photometer,  (-tom'-e-ter).  (Gr.  phos  =  light  4- 
metron  =  measure.)  An  instrument  for  testing 
the  light  sense. 

Photonosus  (fo-ton'-o-sus).  TGr.  phos  =  light -f- 
nosos  =  disease.)  Any  disease  of  the  eye  which 
arises  from  exposure  to  the  glare  of  light. 


Photophobia  (fo-to-fo'-bi-ah).  (Gr.  phos  =  light + 
phobos  =  fear. )     Intolerance  of  light. 

Photopsia  (fo-top'-si-ah).  (Gr.  phos  =  light + 
opsis  =  vision.)  That  condition  in  which  one 
sees  flashes  of  light.  It  is  caused  either  by 
pressure  on  the  eyeballs  or  by  disease  of  the 
brain,  optic  nerve,  or  retina. 

Photoptometer  (fo-top-tom'-e-ter).  (Gr.  phos  = 
light  4-  optos  =  visible  +  metron  =  measure.)  A 
device  for  measuring  sensitiveness  to  light  by 
showing  the  smallest  amount  of  light  that  will 
allow  an  object  to  become  visible. 

Phthisis  Buibi  (tis'-sis).  (Gr.  a  wasting.)  Shrink- 
age of  the  eyeball. 

Physiolog'icaF.     See  physiology. 

Physiology  (fiz-e-ol'-o-je).  (Gr.  physis  =  nature + 
logia  =  discourse.)  That  department  of  nat- 
ural science  which  treats  of  the  organs  of  the 
body  and  their  functions. 

Physostigmine  (fl-so-stig'-min).  The  same  as 
eserin. 

Pla  Mater  (L.  "tender,  affectionate  mother").  The 
innermost  membrane  of  the  brain  and  spinal 
cord,  optic  sheath,  and  capsule  of  Tenon. 

Pigment  (L.  pingere  =  to  paint.)  The  coloring 
matter  in  the  choroid  coat;  the  iris,  etc. 

Pilosebaceous  (pi'-lo-se-ba'-ce-ous).  (L.  pilus  =^ 
hair -f  sebum  =  suet.)  Relating  to  the  hair 
follicles  and  sebaceous  glands. 

Pinguecula  (ping-gwek'-yu-lah).  (L.  pinguis  = 
fat.)  A  small,  yellowish  elevation,  situated  in 
the  conjunctiva  near  the  margin  of  the  cornea. 
Found  in  old  age. 


OPHTHALMTP  nir-nnNAivi^  201 

Pinhole  Disc.  An  opaque  uisc  with  a  pinhole  in 
the  center,  found  in  the  trial  test  case.  It  is 
placed  in  the  trial  frame  quite  close  to  the  eye 
under  examination.  This  perforation  gives  pas- 
sage to  a  small  pencil  of  light  which  passes 
through  the  center  of  the  refracting  media  of 
the  eye.  If  the  patient  can  see  better  through 
the  pinhole,  the  refracting  system  is  at  fault, 
and  vision  can  be  improved  by  glasses.  If,  on 
the  contrary,  vision  is  not  improved,  then  we 
suspect  a  defect  in  the  sensibility  of  the  retina 
or  the  transparency  of  the  media  of  the  eye. 

Pink  Eye.  A  catarrhal  conjunctivitis.  The  eye- 
ball is  of  a  pink  or  reddish  color.  It  is  a  con- 
tagious disease  which  occurs  among  cattle  and 
horses  as  well  as  in  man. 

Pladaro'sis  (Gr.  pladaros  =  flaccid  +  oma  =  tu- 
mor). That  condition  where  there  is  a  soft 
tumor  on  the  eyelid. 

Plane  (L.  planus  =  flat).  When  applied  to  glass. 
a  flat  surface  is  meant.  A  plano-concave  lens 
is  a  lens  having  one  side  concave  while  the 
other  side  is  flat.  A  plane  disc,  or  a  piano,  is 
an  accessory  found  in  the  trial  case  which  has 
two  surfaces,  both  of  which  are  plane. 

Plastic  (plas'-tik).  (Gr.  plastikos  =  form.)  Tend- 
ing to  build  up  tissues. 

Plexus  (plex'-us).  (L.  plectere  =  "to  weave.")  A 
network  or  interjoining  of  nerves  or  vessels. 

Plica  (L.  plicare  =  to  fold).  A  fold.  Applied  to  a 
disease  in  which  the  hairs  become  tangled  and 
glued  together. 

Plica  Semilunaris  (ply'-kah).  A  fold  of  conjunc- 
tiva near  inner  canthus  of  the  eye. 


Point  (L.  punctum).  The  far  point  or  punctum 
remotum  is  the  farthest  point  at  which  the  eye 
can  see  clearly  and  distinctly  with  the  accom- 
modation at  rest.  The  near  point  or  punctum 
proximum  is  the  nearest  point  at  which  the  eye 
can  see  clearly  with  all  of  its  accommodation  in 
use.  P.  of  Reversal.  In  Retinoscopy  the  term 
is  used  to  designate  the  point  between  an  erect 
and  an  inverted  image,  where  the  change  from 
one  to  the  other  occurs.  Where  convergent  rays 
change  to  divergent  rays.  The  myopic  far  point 
in  retinoscopy  is  where  the  movement  of  the 
reflex  appears  neutralized.  In  other  words,  it 
is  that  point  on  one  side  of  which  the  shadow 
movement  is  different  than  on  the  other.  For 
instance,  at  any  position  nearer  the  eye  than 
the  point  of  reversal  the  shadow  will  move 
against  the  mirror,  and  at  any  position  farther 
from  the  eye  the  shadow  will  move  with  the 
mirror.  This  refers  to  the  concave  retinoscope. 
With  the  flat  mirror  the  movement  would  be 
directly  opposite.  P.  of  Fixation.  The  point  for 
which  accommodation  of  the  eye  is  adjusted. 

Polarlmeter  (L.  polaris  =  polar  +  Gr.  metron  =^ 
measure).  An  instrument  for  measuring  the 
rotation  of  polarized  light. 

Polariscope  (L.  polaris  =  polar  +  skopeo  =  I  ex- 
amine). An  instrument  used  in  showing  the 
phenomena  of  the  polarization  of  light. 

Polarization.  The  production  of  a  condition  in 
light  by  virtue  of  which  all  its  vibrations  take 
place  in  one  plane,  or  in  circles  and  ellipses. 

Pole  (L.  polus  =  poIe).  The  summit  of  a  spher- 
ical surface. 


OPHTHALMIC  DICTIONARY  203 

Polychromatic  (pol-y-chro-mat'-ic).  (Gr.  polys  =^ 
many  +  chroma  =  color.)  Possessing  many 
colors. 

Polycoria  (pol-e-ko'-re-ah).  (Gr.  polys  =  many + 
kore  =  pupil.)  The  presence  of  more  than  one 
pupil. 

Polyopia  (pol-e-o'-pe-ah).  (Gr.  polys  =  many + 
ops  =  eye.)     Multiple  vision. 

Polyoptrum  (pol'-y-op'-trum).  (Gr.  polys  =  many 
-f  optos  =  seen.)  A  glass  through  which  ob- 
jects appear  multiplied  but  reduced  in  size. 

Pop-Eyed.    A   large   protruding   condition   of   the 

eyes. 

Pore  (Gr.  "passage").  The  superficial  opening  of 
a  vessel;  one  of  the  small  openings  existing  in 
all  bodies. 

Po'rus  Opticus  (L.  porus  =  pore  +  Gr.  opticus  = 
optic).  The  opening  through  the  lamina  crib- 
rosa  through  which  the  arteria  centralis  retina 
and  veins  pass. 

Positive.  That  condition  which  is  real  and  abso- 
lute. The  positive  surface  of  a  periscopic  lens 
is  tne  convex  surface. 

Posterior  (L.  post  =  after).    Behind;  back. 
Postocular      (L.      post  =  behind  +  oculus  =  eye). 
Posterior  to  the  eyeball. 

Postocular  Neuritis  (L.  post  =  behind  -}-  oculus  = 
eye  +  Gr.  neuron  =  nerve  +  itis).  Inflammation 
of  part  of  optic  nerve  behind  the  eyeball. 

Presbyopia  (pres-by-o'-pi-ah).  (Gr.  presbys  =  old 
+  ops  =  eye.)  When  as  the  result  of  age  the 
power  of  accommodation  has  diminisli-f^d  to  such 
an  extent  that  the  eye   (corrected  for  distance, 


if  ametropic)  cannot  produce  sufficient  accom- 
modation for  the  reading  distance,  the  condi- 
tion is  called  presbyopia.  The  average  age  when 
this  state  of  affairs  is  present  is  45,  and  as  age 
advances  the  accommodation  gradually  dimin- 
ishes and  the  presbyopia  correspondingly  in- 
creases. The  amount  of  presbyopia  is  repre- 
sented by  the  difference  between  the  number  of 
dioptries  of  comfortable  accommodation  present 
and  three  dioptries,  which  must  be  made  good 
by  plus  spheres.  The  presbyope  sees  well  at  a 
distance,  providing  there  is  no  error  of  refrac- 
tion, but  has  difficulty  in  maintaining  good 
vision  for  near  w^ork,  and  the  eyes  become  tired 
after  reading,  especially  at  night.  He  has 
trouble  in  seeing  small  objects  because  he  has 
to  hold  them  far  away,  and  consequently  gets  a 
smaller  visual  angle.  Before  correcting  pres- 
byopia it  is  necessary  to  test  the  patients  dis- 
tant vision  and  correct  any  error  of  refraction. 
Then  place  the  reading  chart  in  his  hand;  if  he 
cannot  read  with  comfort  at  the  distance  he 
wishes  to  hold  it.  add  plus  spheres  of  even 
amount  in  front  of  his  correction  until  you  find 
the  weakest  that  will  allow  comfort  in  reading. 
The  distance  for  which  the  presbyope  requires 
glasses  will  also  vary  much  according  to  his  or 
her  occupation;  ordinarily  it  is  thirteen  inches. 
This  gradual  failure  of  accommodation  is  due 
to  hardening  of  the  crystalline  lens,  loss  of 
power  of  the  ciliary  muscle,  or  both. 

Prescription  (pre-scrip'-shun).  (L.  prae  =  before 
-f  scribere  =  to  write.)  The  formula  for  the 
lenses  required  by  a  patient,  which  are  desig- 


OrHTHALMIC  DICTIONARY  205 

iiated  by  technical  characters  placed  on  blanks 
arranged  for  this  purpose. 

Principal  Focus.  The  focus  of  parallel  rays  of 
light  on  the  principal  axis  after  being  reflected 
or  refracted. 

Principal  Meridians.  The  meridians  of  greatest 
and  least  curvature. 

Principal  Planes.  Straight  lines  which  pass 
through  the  principal  points,  perpendicular  to 
the  principal  axis. 

Prism.  When  applied  to  optics,  is  a  wedge-shaped, 
transparent  body  of  glass  having  two  plane 
sides,  employed  for  the  purpose  of  bending  rays 
of  light.  A  prism  is  not  a  lens,  and  a  ray  of 
light  is  always  bent  towards  its  base.  It  is  used 
in  making  tests  for  muscular  insufficiencies,  and 
sometimes  prescribed  for  constant  wear  in  cases 
of  heterophoria. 

Prisms  are  numbered  by  the  angle  which 
their  surfaces  incline  toward  each  other;  for 
instance,  four  90°  prisms  with  their  bases  and 
apices  placed  together  would  form  a  circle.  The 
bending  power  the  prism  possesses  depends 
upon  the  difference  of  density  of  the  glass  itself 
and  the  medium  which  jt  is  in.  The  ordinary 
prism  is  made  of  crown  glass  and  deviates  a 
ray  of  light  about  half  of  its  own  value;  that  is, 
a  4°  prism  would  deviate  a  ray  of  light  2°. 

Dennett  in  his  method  of  measuring  prisms 
calls  his  unit  the  centrad,  which  is  the  hun- 
dredth part  of  a  radian,  a  radian  being  the 
angle  subtended  at  the  center  of  a  circle  by  an 
arc,  which  is  equal  in  length  to  the  radian. 

Prentice  Method  is  the  prism  dioptry,  which 


is  any  prism  that  has  the  power  to  deflect  a  ray 
of  light  1  cm.  for  each  meter  of  distance. 

These  three  methods  of  numbering  prisms 
differ  very  little  for  low  degrees  in  ophthal- 
mology. 

Rotating  Prisms.  If  two  prisms  of  equal 
strength  be  placed  with  the  base  of  one  over 
the  apex  of  the  other,  they  neutralize  each 
other,  and  if  we  rotate  them  in  opposite  direc- 
tions we  obtain  the  effect  of  any  prismatic  de- 
gree up  to  their  combined  values.  A  prism 
forms  no  image  and  has  no  focus,  and  when 
looked  through,  the  eye  turns  toward  the  apex. 
Deaton  P.,  a  prism  attached  to  a  microscope  to 
give  the  oblique  illumination  for  observing  very 
fine  markings.  Lateral  P.,  an  equal-sided,  total 
reflecting  prism  for  illuminating  a  microscopic 
field. 

Prism-dicptry,  n.  In  Optics,  a  standard  deflection 
of  a  beam  of  parallel  rays  of  light  produced  by 
a  prism.  It  is  equal  to  1  cm.  on  a  tangent  plane 
placed  at  a  distance  of  1  m.  behind  the  prism. 
To  practically  measure  this  deflection  while 
looking  through  a  prism  or  lens,  and  conse- 
quently upon  a  tangent  plane  placed  in  front  of 
the  prism,  it  is  necessary  to  multiply  these 
dimensions  by  six,  in  order  to  insure  parallel 
incidence  of  the  rays  constituting  the  beam  of 
light.  The  prism-dioptry  establishes  a  definite 
relation  between  the  refractive  powers  of  prisms 
and  lenses,  since  "the  prism-dioptries  in  decen- 
tered  lenses  are  in  direct  proportion  to  their 
refractive  powers  and  decentraticn  (see  Decen- 
tration).    The  prism-dioptry  also  bears  a  unique 


OPHTHALMIC  DICTIONARY  207 

relation  to  the  meter  angle  (see  M.  Ang.).  The 
sign  used  to  designate  the  prism-dioptry  is  a 
triangle.  Thus  the  unit,  lA  of  the  dioptral  sys- 
tem is  distinguished  from  1°  of  the  old  degree 
system.  Since  1895  American  lens  manufac- 
turers have  adopted  the  prism-dioptry  as  the 
standard  unit  of  prismatic  power. 

Prismatic  (pris-mat'-ic).  That  which  has  the 
shape  or  effect  of  a  prism.  When  a  lens  is 
decentered  it  will  produce  a  prismatic  effect. 

Prlsmoid  (priz'-moid).  A  body  that  resembles  a 
prism  in  form. 

Prisoptometer  (pris-op-tom'-et-er).  (Gr.  prisma  = 
prism  +  optos  =  seen  +  metron  =  measure.)  An 
instrument  used  for  testing  the  refraction  of 
the  eye  by  means  of  a  revolving  prism. 

Probe.  A  long,  slender  instrument  for  exploring 
wounds.  Lacrimal  P.  is  a  probe  designed  for 
use  on  the  tear  passages. 

Problem  (prob'-lem).  (Gr.  problema  =  a  question 
proposed  for  solution.) 

Product  (prod'-ukt).     (L.  pro  =  forward  -f-  ducere 

^^  to   lead.)      The   result  from  multiplying  one 

number  by  another. 
Progressive  Myopia.    Myopia  that  is  gradually  on 

the  increase. 
Prophthalmos  (prof-thal'-mos).    (L.  pro  =  forward 

-f  ophthalmos  =  eye.)      A    bulging    forward    or 

undue  prominence  of  the  eyeball. 

Proportion  (pro-por'-shun).  (L.  pro  =  before + 
portio  =  share.)  A  proportion  is  an  expression 
of  equality  of  ratios. 


Proptosis  fprop-to'-sis).  (Gr.  pro  =  forward -|- 
ptosis  =  falling.)  A  falling  down  or  sinking  of 
a  part. 

Prosthesis  (Gr.  in  addition  to  +  to  put).  The 
addition  of  an  artificial  part  to  supply  that 
which  is  wanting. 

Prosthesis  Ocularis  (pro-the'-sis).  The  insertion 
of  an  artificial  eye. 

Protractor  Scale  (L.  protrahere  =  to  draw  forth). 
A  device  for  indicating  the  location  of  the  axis 
of  a  cylinder  lens. 

Pseudoblepsis  (seu-do-blep'-sis).  (Gr.  pseudes  = 
false  +  blepsis  =  vision.)  That  condition  in 
which  objects  look  different  from  what  they 
really  are. 

Pseudoglioma  (seu'-do-gly-oh'-mah).  A  circum- 
scribed collection  of  pus  in  the  vitreous. 

Psorophthalmla  (soh-rof-thal'-mee-ah).  (Gr.  pso- 
ros  =  scabby  +  ophthalmos  =  eye.)  That  in- 
flammatory condition  of  the  eye  which  is  accom- 
panied with  itchy  ulcerations. 

Pterygium  (ter-yg'-i-um).  (Gr.  pteryx  =  wing.) 
A  thickening  or  growth  of  the  conjunctiva, 
having  the  appearance  of  a  fly's  wing,  usually 
on  the  nasal  side  of  the  eye,  extending  out 
toward  the  cornea.  It  can  be  removed  by  opera- 
tion, and  should  be  as  soon  as  it  reaches  the 
cornea,  otherwise  it  will  grow  over  it  and  impair 
vision. 

Pterygoid  (ter'-ig-oid).  (Gr.  pteryx  =  wing -f- 
eidos  =  resemblance.)     Wing-shaped. 


\ 


OPHTHALMIC  DICTIONARY  S09 

Ptilosis  (ti-lo'-sis).  That  condition  where  there  is 
a  falling  out  or  loss  of  the  eyelashes. 

Ptosis  (to'-sis).  (Gr.  ptosis  =  a  falling.)  A  droop- 
ing of  the  upper  eyelid.  This  condition  is  caused 
by  paralysis  of  that  branch  of  the  third  or  motor 
oculi  nerve  which  supplies  the  levator  palpebra 
muscle.  It  may  also  be  caused  by  the  thicken- 
ing of  the  upper  lid. 

Puncta  fpunc'-tah).  CL.  punctum  =  a  point.)  A 
small  prominence  or  point.  See  Puncta  Lacri- 
malia. 

Puncta  Lacrimalia  Cpunc'-ta  lak-ri-mal'-i-ah.)  (L. 
punctum  =  point +  lachryma  =  tear.)  Two  small 
openings  near  the  nasal  end  of  the  surface  of 
each  eyelid,  through  which  the  tear  passes  into 
the  lachrymal  canal. 

Punctum  (punc'-tum).  A  fixed  point.  See  Punc- 
tum Remotum  and  Punctum  Proximum. 

Punctum   Remotum.     See  Far  Point. 

Punctum  Proximum.     See  Near  Point. 

Pupil  (pupil).  (From  L.  pupa,  a  babe;  so  called 
from  the  small  image  seen  in  the  eye.)  The 
circular  opening  in  the  iris  through  which  all 
the  rays  of  light  pass  that  have  to  form  an 
image  of  the  object  on  the  retina.  This  aper- 
ture is  dilated  and  contracted  so  as  to  regulate 
the  amount  of  light  entering  the  eye.  The  pupil 
of  man  is  round,  and  by  it  the  anterior  and 
posterior  chambers  of  the  eye  communicate 
with  each  other.  A  contracted  pupil  (myosis) 
indicates  inflammation  of  the  brain;  a  sensitive 
retina,     faculative     hypermetropia,     effect     of 


opium  or  other  drugs.  A  dilated  pupil  (myd- 
riasis) indicates  effect  of  atropine  or  other 
drugs,  myopia,  amblyopia,  absolute  hypermetro- 
pia,  glaucoma,  or  paralysis  of  third  nerve. 

Anisocoria.    Unequal  pupils. 

Corectopia.     Displacement  of  the  pupil. 

Cored isis.  Closure  of  the  pupil  by  a  mem- 
brane, which  causes  loss  of  visual  acuity. 

Coremorphosis.  The  operation  for  artificial 
pupil. 

The  shape  of  the  pupil  is  changed  by  syne- 
chiae,  coloboma,  iridodialysis,  ruptures  of  the 
sphincter  muscle.  The  pupil  appears  black 
when  no  light  returns  through  it  to  the  eye  of 
the  observer.  It  is  more  dilated  in  youth  than 
in  the  aged. 

Pupillary  (pu'-pil-lar-ry).    Pertaining  to  the  pupil. 

Pupillometer  (pu-pil-om'-et-er).  (L.  pupilla  =  pu- 
pil +  Gr.  metron  =  measure.)  An  instrument 
for  measuring  the  diameter  of  the  pupil. 

Pupllloscopy  (L.  pupilla  =  pupil  -f-  skopeo  =  I 
view).    See  Retinoscopy. 

Puplllostatometer       (pu-pil-o-stat-om'-et-er).        (L. 
«  pupilla  =  pupil  +  Gr.  statos  =  placed  +  metron 

=  measure.)     An    instrument    to    measure    the 

distance  between  pupils. 

Pyrkinges  Images.  The  images  seen  on  surface 
of  cornea  and  lens.     See  Catoptric  Test. 

Pyrometer  (py-rom'-e-ter).  (Gr.  pyr  =  fire  +  met- 
ron =  measure.)  An  instrument  for  measuring 
high  degrees  of  heat. 


OPHTHALMIC  DICTIONARY  211 

l^UADRI  LATERAL  (kwod-ri-lat'-e-ral).  (L.  qua- 
tuor  —  four  +  latus  ^=^  a  side.)  A  four-sided 
plane  figure. 

Quantity  (liwon'-ti-ti).  (L.  quantus  =  how  much.) 
Any  amount,  in  measure  or  extent. 

Quiz  CL.  quaesitio  =  inquisition).  Instruction  by 
questions  and  answers.  Q.  Class,  a  body  of  stu- 
dents forming  a  class  for  the  purpose  of  being 
questioned  by  a  teacher.     (See  last  few  pages.) 

Quotient  (kwo'-shent).  (L.  quotiens  =:  how  many 
times.)  The  number  resulting  from  the  division 
of  one  number  by  another. 


R 


ACEMOSE  (ras'-e-mos).  (L.  racemus  =  a 
bunch  of  grapes.)  Bunched;  clustered;  as  in 
staphyloma,  where  the  bulging  occurs  in  several 
places. 

Radiad  (ra'-de-adl.    Towards  the  radial  side. 

Radial   (,ra'-de-al).    Of  or  pertaining  to  the  radius. 

Radian.  An  arc  of  a  circle  which  is  equal  to  the 
radius,  or  the  angle  measured  by  such  an  arc. 

Radiant  (ra'-de-ant).  (L.  radiare  —  to  shine.) 
Diverging,  as  rays  from  a  center. 

Radiation  (ra-di-a'-shun).  Where  rays  of  light 
appear  to  be  thrown  off  from  a  common  center. 

Radius  (L.  "spoke").  The  half  of  the  diameter  of 
a  circle. 

Range  of  Accommodation.  The  distance  of  a  pa- 
tient's vision,  or  the  range  between  the  near 
point  and  the  far  point  of  vision. 


Range  of  Vision.  The  distance  between  the  near 
and  far  point. 

Ratio  (ra'-sho).  (L.,  from  reri,  ratus  =  to  reckon.) 
The  relation  which  one  quantity  or  magnitude 
has  to  another  of  the  same  kind.  It  is  expressed 
by  the  quotient  itself,  making  ratio  equivalent 
to  a  number.  The  term  ratio  is  also  sometimes 
applied  to  the  difference  of  two  quantities  as 
well  as  to  their  quotient,  in  which  case  the 
former  is  called  arithmetical  ratio,  the  latter 
geometrical  ratio.  Ratio  of  a  geometrical  pro- 
gression, the  constant  quantity  by  which  each 
term  is  multiplied  to  produce  the  one  suc- 
ceeding. 

Ray.   The  smallest  imaginary  line  of  light. 

Reciprocal  Numbers  (L,  reciprocus  =  alternating). 
Two  numbers  which  multiplied  together  make 
unity. 

Rectangle  (rek'-tang-gl).  (L.  rectus  =  right  +  an- 
gulus  =  angle.)  A  quadrilateral  all  of  whose 
angles  are  right  angles. 

Rectus  (L.  straight).  Applied  especially  to  cer- 
tain straight  muscles. 

Red-Blindness.  That  condition  in  which  a  person 
is  unable  to  distinguish  red. 

Reduction  (re-duk'-shun).  (L.  re  =  back  +  ducere 
^  to  bring.)  Changing  the  denomination  of 
numbers.  Reduction  Ascending,  changing  to  a 
higher  denomination,  as  from  144  inches  to  12 
feet.  Reduction  Descending,  changing  to  a 
lower  denomination. 

Reflection  fre-flec'-shun),  (L.  re  =  back  +  flee- 
tere  =  to  bend.)     Throwing  back  light.     Reflec- 


OPHTHALMIC  DICTIONARY  213 

tion  from  a  plane  surface  gives  an  erect  imago, 
and  the  angle  of  reflection  is  always  equal  to 
the  angle  of  incidence.  The  image  is  formed  at 
a  distance  behind  the  reflecting  surface  equal  to 
the  (not  so  with  curved  mirrors)  distance  of  the 
object  in  front  of  it,  and  is  called  a  virtual 
image. 

Reflection  by  a  concave  mirror.  Parallel  rays 
falling  on  a  concave  surface  are  reflected  as 
convergent  rays  which  meet  at  a  point  called 
the  principal  focus,  which  is  equal  to  half  the 
radius.  The  distance  of  the  focus  from  the 
mirror  is  called  its  focal  length. 

Reflection  from  a  convex  surface.  Parallel 
rays  falling  on  a  convex  surface  diverge  and 
never  meet.  No  matter  what  the  position  of 
the  object  before  a  convex  mirror,  the  image  is 
always  virtual,  erect,  and  smaller  than  the 
object. 
Reflector  (re-flec'-tor).  A  device  for  reflecting 
light. 

Refracting  Media  (see  Media).  R.  System.  A  lens, 
or  combination  of  lenses,  for  the  creation  of 
optical  images. 

Refraction  (re-frac'-shun),  (L.  re  =  back  +  fran- 
gere  =  to  break.)  The  bending  of  a  ray  of 
light  in  passing  obliquely  from  one  medium  to 
another  of  different  density.  This  bending  is 
caused  by  one  side  of  the  ray  having  its  speed 
increased  or  decreased  according  to  the  density 
of  the  second  medium.  Refraction  never  takes 
place  in  any  one  medium,  but  between  the 
media.  Light  in  passing  from  a  rarer  to  a 
denser  medium  is  bent  toward  the  perpendicu- 
lar, and  from  a  denser  to  a  rarer  is  bent  away 


from  the  perpendicular.  Double  R.,  refraction 
in  which  the  incident  ray  is  divided  into  two 
refracted  rays.     Static  R.,  refraction  of  the  eye 


J 


A%  It  emerges 


REFRACTION  BY  PLANE  SURFACE. 

No.  1  ray  of  light  is  called  the  incident  before  entering  the 
second  medium.  A  ray  passing  from  a  rarer  lo  a 
denser  medium  is  refracted  towards  the  perpendicular, 
as  shown  in  the  above  cut.  The  ray  BA  is  refracted 
on  striking  the  glass  MM,  and  again  refracted  on 
emerging.  In  passing  from  a  denser  to  a  rarer  me- 
dium, the  ray  is  refracted  from  the  perpendicular. 
P. represents  a  ray  falling  perpendicular  to  the  surface 
separating  the  two  media.  It  continues  its  course 
without    undergoing    any    refraction. 

No.  2  represents  the  reflected  ray.  The  angle  formed  by 
the  incident  ray  with  the  perpendicular  is  always  equal 
to  the  angle  of  reflection. 

The  dotted  line  marked  BA'  represents  the  course  the 
No.   1  ray  would  have  taken  had  it  not  been  refracted. 

The  side  of  the  incident  ray  marked  B  will  be  found  at 
R  in  the  reflected  ray,  and  A  at  F, 


at  rest.     Dynamic  R.,  refraction  of  the  eye,  plus 
that  secured  by  accommodation. 

Absolute  index  of  Refraction  is  that  which  is 


OPHTHALMIC  DICTIONARY  215 

found  when  light  passes  from  a  vacuum  into  a 
given  medium. 

Refraction ist  (re-frac'-tion-ist).  One  who  is  skilled 
in  correcting  errors  of  refraction  of  the  eye. 

Refractive  (re-frac'-tive).    Pertaining  to  refraction. 
Refractometer  (re-frak-tom'-e-ter).   An  instrument 
for  measuring  refraction. 

Regular  (reg'-u-lar).  (L.  regula  =  a  rule,)  Accord- 
ing to  rule;  normal. 

Relative  Index  of  Refraction  is  that  which  is 
found  when  light  passes  from  atmospheric  air 
into  another  medium. 

Relax  (L.  re  =  back  +  laxare  =  to  loosen).  To 
loosen,  to  slacken. 

Relaxa'tion.    A  lessening  of  tension. 

Remedy  (L.  re  =  again  +  mederi  =  to  heal).  Any- 
thing acting  as  a  cure  for,  or  the  relief  from, 
unhealthy  conditions. 

Reposition  (re-po-zi'-shun).  (L.  repositus  =  to  lay 
up.)  The  act  of  putting  back  in  a  normal 
position. 

Retina  (ret'-in-a).  (L.  rete  =  a  net.)  On  the  inner 
surface  of  the  choroid,  and  closely  in  contact 
with  it,  we  find  the  internal  or  third  and  most 
important  of  the  ocular  tunics,  the  retina;  to 
which,  indeed,  the  other  two  are  merely  protec- 
tive or  containing  membranes.  The  retina  is  the 
immediate  continuation  of  the  optic  nerve,  which 
extends  from  the  brain  to  the  eyeball,  perfo- 
rates the  sclerotic  and  choroid,  and  immediately 
spreads  out  into  a  thin  lamina  over  the  surface 
of  the  latter,  and  is  attached  at  two  points  only 
— at  the  entrance  of  the  optic  nerve  and  at  its 


most  anterior  border,  the  ora  serrata.  The  point 
of  entrance  of  the  optic  nerve,  which  is  known 
as  the  optic  disc,  is  nearly  on  the  horizontal 
meridian  of  the  globe,  and  about  one-tenth  of 
an  inch  to  the  nasal  side  of  the  posterior  pole, 
so  that  it  is  the  left  eye  which  is  represented  in 


RETINA, 
a — macula    lutea,    the    most    sensitive    part    of    the    retina. 

the  cut  under  Anatomy.  The  function  of  the 
retina  is  to  receive  the  pictures  which  are 
formed  within  the  eye  by  means  of  the  waves 
of  light  reflected  from  objects,  and,  through  the 
medium  of  the  optic  nerve,  to  transmit  the 
resulting  visual  impressions  to  the  brain. 

Just  as  the  sense  of  touch  is  not  diffused  uni- 
formly over  the  surface  of  the  body,  but  is  more 
acute  in  some  parts — for  instance,  the  finger 
tips — than  in  others,  so  also  the  retina  is  not 
equally  sensitive  to  the  luminous  impressions 
over  its  whole  surface,  but  in  the  highest  de- 
gree a  little  to  the  temple  side  of  the  posterior 
pole,  in  a  part  known  as  the  macula  lutea,  or 
yellow  spot,  which  may  be  considered  the  real 
center  of  the  retina,  yet  it  is  to  one  side.  From 
this  spot  the  sensitiveness  gradually  diminishes 
to  its  most  anterior  edge.    The  retina  does  not 


OPHTHALMIC  DICTIONARY  217 

extend  as  far  forward  as  the  choroid,  but  termi- 
nates a  little  in  front  of  the  equator,  at  the 
posterior  border  of  the  ciliary  body,  in  a  saw- 
like margin,  the  rough  edge  of  which  is  known 
as  the  era  serrata. 

Structures  of  the  Retina  According  to  Gray. 
From  within  outward,  the  layers  of  the  retina 
are  named  as  follows: 

1.  Membrana  limitans  interna, 

2.  Fibrous  layer,  consisting  of  nerve  fibers. 

3.  Vesicular  layer,  consisting  of  nerve  cells. 

4.  Inner  molecular,  or  granular  layer. 

5.  Inner  nuclear  layer. 

6.  Outer  molecular,  or  granular  layer. 

7.  Outer  nuclear  layer. 

8.  Membrana  limitans  externa. 

9.  Layer  of  rods  and  cones,  or  Jacob's  Mem- 
brane. 

10.  Pigmentary  layer. 
Retinal    Reflex.    A    term    used    in    retinoscopy   to 
designate  the  light  reflected  from  the  retina  and 
creating  the  light  in  the  pupil. 

Retinitis  (ret-in-i'-tis).  (L.  retina  +  Gr  ,  itis  = 
inflammation.)  Inflammation  of  the  retina.  It 
is  characterized  first  of  all  by  a  diffused  cloudi- 
ness of  the  organ.  The  cloudiness  varies  very 
greatly  in  intensity,  although  in  general  it  is 
greatest  in  the  vicinity  of  the  optic  disc,  because 
here  the  retina  is  thickest.  Consequently,  the 
outlines  of  the  optic  disc  become  indistinct  and 
the  vessels  in  the  retina  hazy.  The  function  of 
the  retina  is  impaired  in  proportion  to  the  in 
tensity  and  extent  of  the  inflammation.  In  the 
lightest  cases  vision  may  be  normal,  so  that  the 
patients  complain  simply  of  the  presence  of  a 


light-colored  cloud  before  their  eyes.  But  for 
the  most  part  vision  is  very  considerably  re- 
duced, both  because  of  the  changes  in  the  retina 
itself  and  because  of  the  accompanying  opac- 
ities in  the  vitreous.  The  course  of  retinitis  is 
always  rather  sluggish.  It  is  only  in  the  lightest 
cases  that  the  inflammation  abates  completely 
within  a  few  weeks,  and  then  the  visual  acuity 
may  once  more  become  perfectlj'  normal.  But 
for  the  most  part  it  takes  several  months  for  all 
the  inflammatory  symptoms  to  disappear  from 
the  retina,  while  the  sight  remains  permanently 
impaired.  Severe  and,  more  particularly,  recur- 
rent inflammations  of  the  retina  lead  to  atrophy 
of  it,  pigmentation  frequently  occurring  at  the 
same  time  (through  migration  of  pigment  from 
the  pigment-epithelium).  When  atrophy  of  the 
retina  has  once  made  its  appearance,  the  sight 
is  always  destroyed,  either  completely  or  all 
except  a  small  remnant,  and  its  restoration  is 
no  longer  possible. 

Retinoscope  (ret'-in-o-scope).  An  instrument  with 
which  an  objective  examination  of  the  dioptric 
state  or  condition  of  the  eyes  may  be  measured. 
(Made  in  plane  and  concave.) 

The  concave  can  be  combined  with  a  strong 
plus  lens,  about  20-D.,  and  used  as  an  ophthal- 
moscope. There  is  also  a  difference  in  the  move- 
ment of  the  shadow  in  retinoscopy.  In  working 
with  the  plane  mirror  between  53  and  60  inches, 
the  movement  is  against  in  myopia  of  .75  or 
more,  while  in  hypermetropia,  emmetropia,  or 
less  than  .75  of  myopia  the  shadow  moves  with 
the  mirror.  With  the  concave  it  is  just  the  re- 
verse;  the  shadow  in  hypermetropia,  emmetro- 


OPHTHALMIC  DICTIONAllV  :il9 

pia,  and  a  small  amount  of  myopia  will  go 
against  the  mirror.  In  more  than  .75  of  myopia, 
the  movement  will  be  with  the  mirror. 

It  makes  no  difference  which  you  use.  the 
findings  will  be  the  same,  and  you  deduct  from 
plus  and  add  to  minus  findings  the  same 
amounts;    it  depends   on  the  distance  you  are 


Hand    Retinoseope. 

sitting  from  the  patient.  When  sitting  at  a  lit- 
tle over  40  inches,  you  subtract  one  dioptry  from 
all  plus  findings,  and  add  minus  .75  to  all  minus 
findings.  When  working  between  53  and  60 
inches,  you  subtract  .75  from  all  plus  findings 
and  add  minus  .50  to  all  minus  findings. 
Retinoscopy  (ret-in-os'-co-py).  (L.  retina  +  scopeo 
=- 1  examine.)  "Skiametry."  Retinoscopy,  or 
the  Shadow  Test,  is  one  of  the  methods  of  esti- 
mating the  refraction  of  the  eye.  We  examine 
the  movements  of  the  shadow  when  the  fundus 
is  illuminated  by  light  thrown  into  the  eye  from 
a  mirror. 

With  the  Concave  Mirror.  The  patient  is 
seated  in  a  dark  room,  with  the  light  placed  a 
little  above  the  head,  and  far  enough  back  so 
that  it  will  throw  no  direct  rays  upon  his  face. 
It  is  best  to  use  a  shade  around  the  light  to 
prevent  it  from  illuminating  the  walls  of  the 
room,  having  a  hole  an  inch  in  diameter  in  the 


front  and  about  the  center  of  the  flame.  We 
will  now  begin  with  the  examination. 

In  examining  the  right  eye  have  the  patient 
look  across  your  right  shoulder,  and  in  exam- 
ining the  left  have  him  look  over  your  left 
shoulder. 

Once  in  a  position  to  begin  the  test,  we  reflect 


the  light  from  the  mirror  across  several  merid- 
ians of  the  patient's  eye,  at  the  same  time  watch- 
ing the  reddish  fundus  reflex  in  the  pupil.  If 
the  movement  of  the  fundus  reflex  is  against  that 
of  the  mirror  in  any  one  meridian,  put  a  plus 
sphere  before  the  eye,  and  continue  to  increase 
its  strength  until  you  find  the  weakest  lens  that 
will  reverse  the  last  meridian,  whose  movement 
was  against  that  of  the  mirror. 

If  there  is  no  astigmatism  the  reflex  will  be 
equally  bright  in  all  its  parts  like  a  small  full 


OPHTHALMIC  DICTIONARY  221 

moon.  On  the  other  hand,  if  there  is  any  astig- 
matism the  shadow  will  have  a  band  or  ribbon- 
like appearance,  the  sphere  being  a  finding  for 
the  meridian  of  the  band. 

We  next  proceed  to  correct  the  meridian  at 
right  angles  to  the  band,  using  a  minus  cylinder 
(on  account  of  the  movement  being  with  that 
of  the  mirror)  with  its  axis  over  the  band,  and 
continue  to  increase  its  strength  until  we  find 
the  weakest  that  will  open  up  the  band  until  the 
reflex  is  round  in  appearance. 

Prom  the  sphere  now  before  the  eye  we 
deduct  the  power  of  a  lens  that  will  focus  at 
the  distance  the  mirror  was  held  from  the 
patient's  eye.  What  is  left  of  the  sphere  com- 
bined with  the  cylinder  is  the  patient's  Rx. 

Myopia:  On  the  other  hand,  if  the  shadow 
moves  with  in  all  meridians,  put  on  a  weak 
minus  sphere  and  increasing  its  strength  until 
we  find  the  weakest  that  will  about  reverse  the 
shadow  in  any  one  meridian.  If  there  is  no 
astigmatism  the  shadow  will  move  the  same  in 
all  meridians  and  have  .the  appearance  of  a  full 
moon.  If  there  is  any  astigmatism  the  reddish 
fundus  reflex  will  have  a  ribbon-like  appearance 
(the  narrower  the  band  the  higher  the  amount), 
the  sphere  always  being  the  finding  for  the 
meridian  in  which  the  band  is  seen.  The  merid- 
ian at  right  angles  to  the  band  is  still  moving 
with  the  movement  of  the  mirror  and  a  minus 
cylinder  with  its  axis  over  the  band  is  used  to 
reverse  it  while  moving  the  mirror  across  the 
band. 

To  the  sphere  already  in  the  trial  frame  we 
add  a  minus  sphere  that  will  focus  at  the  dis- 


taiice  we  are  holding  the  mirror  from  the  eye 
of  a  patient. 

In  writing  the  Rx,  put  down  what  is  left  of 
the  sphere  after  deducting  or  adding  for  the 
working  distance,  combining  with  it  the  full 
power  of  the  cylinder,  placing  its  axis  at  the 
degree  the  scratch  on  the  lens  points  to  on  the 
trial  frame. 

If  the  above  directions  are  followed  plus  cyl- 
inders will  never  be  used. 

The  larger  the  error  the  slower  the  movement 
will  be.  Large  errors  are  easier  than  small  ones 
to  detect  and  correct  with  the  retinoscope. 

Prove  up  your  retinoscopic  test  subjectively. 
If  more  plus  can  be  added  or  less  minus  given 
without  interfering  with  the  vision,  make  the 
change. 

In  using  the  plane  mirror  follow  above  direc- 
tions, but  use  plus  when  the  shadow  moves  with 
and  minus  if  against. 

When  the  light  that  is  coming  from  the'  pa- 
tient's eye  (after  reflection  by  the  retina)  focuses 
in  front  of  the  operator  the  shadow  will  move 
with  the  movement  of  the  concave  mirror.  On 
the  other  hand,  if  these  rays  of  light  pass  the 
operator  without  focusing,  the  movement  will 
be  against  that  of  the  mirror. 

The  shadow  moves  against  in  Hypermetropia, 
Emmetropia  and  small  amounts  of  Myopia.  If 
the  operator  is  working  at  41"  the  eye  must 
have  one  dioptre  or  more  of  Myopia  for  the 
shadow  to  move  with  the  movement  of  the 
mirror. 

On  page  223  are  two  cuts  showing  the  fundus 
reflex    in    the    pupil.      The    reflex    shows    white 


OPHTHALMIC  DICTIONARY  223 

instead  of  red  as  it  really  is  but  they  will  answer 
the  purpose;  the  first  is  round  on  the  edge  like 


""^Efe.  ¥S?p-'5'5Jaj9UA 


a  full  moon,  indicating  no  sign  of  astigmatism, 
while  the  second  is  ribbon  or  band  like,  showing 
there  must  be  astigmatism  between  the  90th 
and   180th  meridians   in  this   case. 


Retractor  (re-trac'-tor).  An  instrument  used  for 
drawing  and  holding  the  parts  away  while 
undergoing  an  operation,  or  for  any  otlier 
purpose. 

Retrobulbar  (re-tro-bul'-bar).  (L.  retro  =  behind 
+  bulbus  =  bulb.)  That  which  is  situated  or 
occurring  behind  the  eyeball. 

Retrobulbar-Neuritis.  Inflammation  of  the  optic 
nerve  behind  the  globe  of  the  eye. 


Reversal  Point.  This  term  is  used  Iri  retinoscopy 
to  describe  the  change  of  movement  of  the 
shadow.  For  instance  if  the  rays  of  light 
which  are  coming  from  the  patient's  eye  focus 
behind  the  operator  the  shadow  will  always 
move  against  the  movement  of  the  concave 
mirror,  if  they  are  made  to  converge  by  the 
aid  of  a  plus  lens  so  as  to  focus  just  in  front 
of  the  operator,  the  movement  will  be  with 
that  of  the  mirror,  making  it  the  point  of 
reversal. 

Rheum  (rume).  (Gr.  rheuma  =  a  flux.)  A  watery 
discharge  from  the  eyes. 

Rheumatic  Iritis.     Iritis  caused  by  rheumatism. 

Rhodopsin  (rho-dop'-sin).  (Gr.  rhodon  =  rose + 
ops  =  eye.)  Visual  purple;  pigment  of  outer 
segment  of  retinal  rods. 

Rhytidosis  (rit-id-o'-sis.)  (Gr.  rhytidosis  =  a  wrin- 
kling.)    A  wrinkling,  as  of  the  cornea. 

Riolanis  Muscle.  An  involuntary  muscle  used  in 
closing  the  eye.  It  reinforces  the  orbiculars 
and  brings  the  margin  of  the  lids  closer  to- 
gether. 

Rod.  Relates  to  tlie  retina.  It  is  one  of  the  cell 
elements  of  which  Jacob's  Membrane  is  com- 
posed. These  minute  bodies  are  cylindrical  in 
form,  hence  the  term,  rod  (rods  and  cones). 

Rodent  Ulcer.  A  -destructive  ulcer  beginning  at 
the  margin  of  the  cornea.  It  is  confined  to  the 
surface,  not  ^omg  deeper  than  Bowman's 
Membrane.     First  (described  by  Dr.  Mooren. 

Roentgen  Rays.  A  forna  of  X  rays  used  in  deter- 
mining the  presence  and  also  the  exact  position 
of  foreign  bodies  ?in  ithe  eyeball  or  orbit. 


OPHTHAI^MIC  DICTIONARY  225 

Romberg's  Symptoms  (Moritz  Heinrich  Romberg, 
Berlin  physician,  1795,  1873).  Difficulty  in  stand- 
ing when  the  eyes  are  shut:  a  sign  of  loco- 
motor ataxia. 

Rota'tion  (L.  rota  =  a  wheel.)  Process  of  turning 
around  an  axis.  R.  of  the  Mirror.  A  term  used 
in  retinoscopy  to  indicate  the  movement  of  the 
mirror  to  create  a  movement  of  the  light  area. 

Ru-biform.     Having  the  form  or  nature  of  red. 

Rubify.     To  redden. 

Ruischiana  Membrane.  The  third  or  chrio- 
capillaris  membrane  of  the  choroid. 

Rutilant.     Glittering,  shining. 

RULES 

To  find  the  deviating  power  of  a  prism,  multiply 
the  difference  of  index  by  the  number  of  de- 
grees of  prism. 

To  find  meter  curve  of  a  lens  divide  dioptric 
power  by  difference  of  index. 

To  find  meter  curve  of  a  lens  divide  one  meter 
by  the  radius  of  curvature  on  lens. 

To  find  difference  of  in^dex  divide  power  of  the 
lens  by  the  meter  curves  of  its  radius. 

Refractive  power  of  a  lens  depends  upon  its  curva 
ture  and  the  index  of  refraction  of  the  glass 
combined.  An  increase  of  either  one  will  pro- 
duce greater  refracting  power.  The  shorter  the 
focal  length  the  greater  the  refractive  power. 

To  find  focal  length  of  a  lens  surface  divide  the 
radius  of  curvature  by  difference  of  index. 

To  Convert — 

Dioptries    to   meters   of   focal   length,    divide 
1  by  the  number  of  dioptries. 
Meters    of    focal    length    to    dioptries,    divide 
1  by  the  number  of  meters. 


-  Dioptries  to  centimeters  of  focal  length,  divide 
100  by  the  number  of  dioptries. 

Centimeters  of  focal  length  to  dioptries,  divide 
100  by  the  number  of  centimeters. 

Dioptries  to  inches  of  focal  length,  divide  40 
by  the  number  of  dioptries. 

Inches  of  focal  length  to  dioptries,  divide  40 
by  the  number  of  inches. 

To  find  dioptric  value  of  any  surface,  multiply  the 
difference  of  the  index  of  refraction  by  the 
number  of  meter  curves  in  the  radius  of  curva- 
ture and  give  it  the  sign  of  the  curve  of  the 
denser  media.  Remember  two  meter  curves  in 
optics  mean  one-half  and  three  meter  curves, 
one-third  of  a  meter,  and  so  on. 
To  find  the  angle  of  refraction,  divide  the  angle 
of  incidence  by  the  index  of  refraction  of  the 
second  media. 
To  find  the  radius  of  curvature  of  any  media, 
multiply  the  focal  length  desired  by  the  differ- 
ence of  the  index  in  the  two  media. 

Index  of  Refraction  =  Angle  of  Incidence  di- 
vided by  Angle  of  Refraction. 

Angle  of  Incidence  =  Angle  of  Refraction 
multiplied  by  Index  of  Refraction. 

Focal  Length  of  Curved  mirrors  =  one-Jialf  of 
the  radius. 

Power  of  a  Mirror  =  one  meter  divided  by  its 
focal  length  (catoptries). 

Metric  Curve  of  a  Mirror  =  one  meter  divided 
by  the  radius  of  the  mirror. 

Radius  of  Mirror  =  one  meter  divided  by  the 
metric  curve  of  the  mirror. 
To  find  the  dioptry  power  in  any  meridian  of  a 
cylinder,  take  the  distance  between  the  merid- 


OPHTHALMIC  DICTIOXARY  227 

lan  of  which  you  wish  to  know  the  power  and 
the  axis  of  the  cylinder,  multiply  it  by  the 
power  of  the  cylinder,  and  divide  by  90. 

To  find  the  number  of  millimeters  to  decenter  a 
lens  for  prismatic  effect,  multiply  the  prism 
wanted  by  10  and  divide  by  the  power  of  the 
lens. 

When  prismatic  effect  is  wanted  in  both  the 
horizontal  and  vertical  meridians,  one  prism  can 
be  used  by  placing  a  prism  obliquely. 

To  find  the  prism  to  prescribe,  square  the  power 
of  the  original  prisms  and  add.  Extract  the 
square  root  of  the  sum,  which  will  give  you  the 
power  of  the  new  prism. 

To  find  the  meridian  to  place  the  base  of  the  new 
prism,  divide  90  by  the  combined  power  of  the 
original  prisms  and  multiply  by  the  vertical 
prism;  this  gives  the  distance  from  horizontal 
to  place  the  base  of  the  new  prism. 

To  find  the  size  of  the  image,  focal  length  of 
emergent  wave  multiplied  by  size  of  object 
divided  by  focal  length  of  incident  wave;  or. 
dioptric  value  of  incident  wave  multiplied  by 
size  of  object  divided  by  dioptric  value  of  the 
emergent  wave. 

To  find  the  size  of  the  object,  reverse  the  formula 
above. 

To  find  the  size  of  the  image  on  the  retina,  multi- 
ply the  size  of  the  object  by  the  distance  be- 
tween the  nodal  points  and  the  retina,  then 
divide  by  the  distance  between  the  nodal  points 
and  the  object. 

To  find  circumference  of  a  circle,  multiply  diam- 
eter by  3.1416. 


To  find  diameter  of  a  circle,  multiply  circumfer- 
ence by  .31831. 

To  find  area  of  a  circle,  multiply  square  of  diam- 
eter by  .7854. 

To  find  area  of  a  triangle,  multiply  base  by  one- 
half  perpendicular  height. 

To  find  surface  of  a  ball,  multiply  square  of 
diameter  by  3.141 1;. 

RULES  TO  BE  REMEMBERED 

No.  1.  No  eye  should  be  allowed  to  use 
accommodation  at  20  feet  or  more. 

No.  2.  Always  give  a  hyperope  the  strongest 
plus  that  will  not  blur  his  best  distant  vision. 

No.  3.  Give  a  myope  the  weakest  minus  that 
will  give  him  best  vision.  Never  put  minus 
where  it  does  not  show  returns. 

No.  4.  After  putting  the  patient  in  the  fog. 
place  the  axis  of  your  minus  cylinder  at  right 
angles  to  the  plainest  line  seen. 

No.  5.  Correct  presbyopia  after  correcting 
distant  vision. 

No.  6.  Before  testing  for  muscle  trouble  cor- 
rect the  ametropia. 


(2 

i^AC   (L.  saccus  =   a  bag).     A  bag-like  organ. 

Saemisch's  Ulcer  ( sa'-misb-ez).  (Edwin  Theodor 
Saemisch.  Australian  ophthalmologist.  1833.) 
Infectious  corneal  ulcer. 

Sarcoma  (sar-ko'-mah ).  (Gr.  sarx  ^  flesh  +  oma 
=  tumor.)  A  tumor  made  up  of  a  substance 
like  the  embryonic  connective  tissue.  It  is 
often  hijrhly  malignant.     Sarcoma  of  the  ciliary 


OPHTHALMIC  DICTIONARY 


220 


body  is  generally  pigmented,  and  often  passes 
unobserved  until  it  attains  considerable  size  as 
a  brown  mass,  which  was  at  first  concealed 
from  view  by  the  iris.  Occasionally  it  makes 
its  first  appearance  at  the  angle  of  the  anterior 
chamber. 

Schematic     Eye     (ske-mat'-ik).      (Gr.     schema  = 
shape,  outline,  plan.)     A  model  or  drawing  that 


represents  a  normal  or  emmetropic  eye.    Used 
in  demonstrating  optical  laws. 

Schlemm's  Canal  for  circular  venous  sinus). 
(Friedrich  Schlemm,  German  anatomist,  ]795- 
1858.)  A  ring-like  canal,  of  0.3  by  0.-5  mm. 
diameter,  in  the  first  tunic  of  the  eye,  between 
the  cornea  and  the  sclerotic.  By  means  of  the 
Spaces  of  Fontana  it  connects  with  the  anterior 
chamber  on  one  side,  and  directly  communi- 
cates with  the  anterior  ciliary  veins  on  the 
other. 

The  Spaces  of  Fontana  are  formed  by  the 
dividing  of  the  tissue  from  Descemet's  Mem- 
brane in  crossing  from  the  corneal  margin  to 
pass  into  the  base  of  the  iris,  and  constitute 
the  ligament  pectinatum  iridis. 


i^LU  »*  io    I  v^v^  r\  1  . 


Scintillation  rsoin-til-la'-shun  ).  (L.  scintilla  ^^  a 
spark  J    A  sensation  of  sparks  before  the  eye. 

Scissors  Movement.  A  peculiar  movement  of  the 
retinal  reflex,  resembling  the  opening  and  shut- 
ting of  a  pair  of  scissors.  It  indicates  a  condi- 
tion of  irregular  astigmatism. 

Sclera  Cskle'-ra).  (Gr.  skleros  ^  hard.;  The  ex- 
ternal and  white  coat  of  the  eyeball,  The  scle- 
rotic. 

Scleral.     Pertaining  to  the  sclera. 

Sclerectasia  Tskle-rec-ta'-si-ahj.  CGr.  sclera  -r  ek- 
tasia  ^- an  extension.)  A  bulging  state  of  the 
sclera. 

Sclerectomy  (skle-rek'-to-myj.  fOr.  skleros  = 
hard  -  ektome  =  excision. j  Excision  of  a  por- 
tion of  the  sclera. 

Sclerectasis  Cskle-rek'-ta-sis).  A  protrusion  of  the 
.sclerotic  coat.     See  Staphyloma. 

Scleriritomy  Cskle-rir-it'-o-myj.  (Gr.  skleros  = 
hard  -f-  iris  +  tome  ==  excision.)  Incision  of  the 
sclera  and  iris  in  anterior  staphyloma. 

Scleritis  Cskle-ri'-tis).  CGr.  skleros  ^  hard  —  ilis 
-  inflammation.)  Inflammation  of  the  sclerotic 
coat. 

Sclerochoroiditis  Tskle-ro-cho-roid-i'-tis).  Inflam- 
mation of  both  the  choroid  and  the  sclerotic 
coats  of  the  eye. 

Scleroconjunctival  rskle-ro-con-junc-ti'-valj.  That 
condition  in  which  the  sclera  and  the  conjunc- 
tiva are  concerned. 

Sclerocorneal  Sulsus  ffurrow).  The  angle  or  de- 
pression formed  by  the  difference  in  the  radius 
of  curvature  of  the  sclerotic  and  cornea.    This 


OPHTHALMTO  DICTIONARY  231 

angle  makes  the  eyeball  stronger  and  more  firm 
at  this  point,  and  it  is  just  inside  this  angle  that 
the  ciliary  muscles  are  attached. 

Sclerocorneal  (skle-ro-cor'-ne-al).  Relating  to  the 
sclerotic  coat  and  cornea. 

Sclerolritis  (skle-ro-i-ri'-tis).  An  inflammation 
which  involves  both  the  iris  and  the  sclera. 

Sclerokeratolri'tis.  Inflammation  of  the  sclera, 
cornea,  and  iris. 

Scleronyxis  (skl'e-ro-nyx'-is).  (Gr.  skleros  hard 
4- nyxis  a  pricking.)  A  perforation  of  the 
sclerotic  coat. 

Sclerophthalmia  (skle-rof-thar-mi-ah).  (Gr.  skle- 
ros =  hard  4  ophthalmos  =  eye.)  That  condi- 
tion in  which  the  sclera  overlaps  the  cornea,  so 
that  only  a  portion  of  the  latter  remains  clear. 

Scle'rosed  (Gr.  skleros  =  hard).  That  condition  in 
which  a  part  is  affected  with  sclerosis;  a 
hardening. 

Sclerosis  (sclero'-sis).  (Gr.  sklerosis  =  hardness.) 
The  process  of  becoming  hard,  tough,  or  in- 
durated. 

Sclerotic  (skle-rot'-ic).  (Gr.  skleros  =  hard.)  The 
posterior  five-sixths  of  the  first  tunic.  It  is 
firm,  hard,  and  opaque;  known  as  the  white  of 
the  eye.  It  serves  to  give  shape  to  the  globe, 
protects  its  more  delicate  interior,  and  at  the 
same  time  acts  as  a  dark-box  or  camera.  It  is 
to  this  coat  that  the  muscles  are  attached.  Th(^ 
sclerotic  is  thickest  in  the  posterior  part,  where 
it  has  a  thickness  of  about  1  mm.  It  gradually 
diminishes  in  thickness  toward  the  anterior 
part,  becoming  somewhat  thicker  near  the  cor- 


nea,  because  here  the  tendons  of  the  recti 
muscles  are  attached  and  fused  with  it.  The 
sclerotic  consists  of  fine  cotton-like  fibers  or 
connective  tissues,  which  are  united  into  bun- 
dles which  seem  'to  be  woven  in  all  directions. 
Between  the  bundles  are  found  lymph-spaces, 
which  are  in  part  lined  with  fat  cells.  The 
sclera  has  very  few  blood-vessels  and  nerves. 
The  blood-vessels  are  derived  from  the  anterior 
ciliary  and  posterior  ciliary  arteries.  The  venous 
blood  is  removed  by  the  venae  vorticosae  and 
the  anterior  ciliary  veins.  Its  nerves  are  de- 
rived from  the  ciliary  nerves. 

Scleroticectomy  (skler-ot-i-kek'-to-my).  (Gr.  skle- 
ros  =  hard  +  ektome  =  excision.)  An  operation 
for  artificial  pupil  by  removal  of  a  portion  of 
the  sclerotic. 

Sclerotomy  (skle-rot'-o-me).  (Gr.  skleros  =  hard 
+  tome  =  incision.)  Surgical  incision  of  the 
sclera. 

Scotodinia  (sko-to-din'-iah).  (Gr.  skotos  =  dark- 
ness -|-  dine  =  a  whirling.)  Dizziness,  with  head- 
ache and  dimness  of  vision. 

Scotoma  (sko-to'-mah).  (Gr.  skotoma  =  darkness.) 
That  condition  in  which  there  is  a  blind  or  par- 
tially blind  area  in  the  visual  field.  Sometimes 
the  patient  will  complain  of  seeing  dark,  vanish- 
ing, cloudy  spots  before  the  eyes.  Absolute  S.,  a 
part  of  the  visual  field  in  which  there  is  absolute 
blindness. 

Scotometer  (sko-tom'-e-ter).  An  instrument  for 
measuring  scotoma. 

Sebaceous  Cysts  (L.  sebum  =  suet  -f  Gr.  kystis  = 
bladder.)    A  small  rounded  body,  the  size  of  a 


OPHTIJALMIC  DICTIONARY  233 

pea,   which  appears   in  the  thicker   portions  of 
the  skin  of  the  eyelids. 

Seborrhea  (seb-or-e'-ah).  (L.  sebum  =  suet  -f  Gr. 
rhoia  =  a  flow.)  An  abnormal  secretion  of  the 
sebaceous  glands. 

Se'cant  (L.  secare  =  to  cut).  (Geometry.)  A 
line  that  cuts  another,  or  divides  it  into  parts. 
The  secant  of  a  circle  is  a  line  drawn  from  the 
circumference  on  one  side  to  a  point  on  the  out- 
side of  the  circumference  on  the  other. 

Secondary  Axis.     See  Axis. 

Secondary  Foci.     See  Focus. 

Seg'ment  (L,  segmentum;  secare  ^^  to  cut).  A 
section  of  a  circle.  A  cylindrical  lens  is  a  seg- 
ment of  a  cylinder  which  refracts  rays  of  light 
in  all  meridians  but  one.  This  meridian  is  known 
as  the  axis.  A  spherical  lens  is  a  segment  of  a 
sphere.  A  segment  of  anything  is  one  of  the 
parts  into  which  it  is  divided. 

Serpiginous  (ser-pij'-in-us).  (L.  serpere  =  to 
creep.)    Resembling  a  ringworm. 

Shadow  Test.     See  Retinoscopy. 

Sheath.  A  tubular  case  or  envelope.  Optic  S., 
the  covering  of  the  optic  nerve  formed  by  the 
dura  mater  on  the  outside,  and  the  pia  mater 
on  the  inside,  of  the  subarachnoid  space. 

Shortsightedness.    See  Myopia. 

Sight.  The  sense  by  which  external  objects  are 
located  and  seen,  their  color,  size,  and  form 
described,  as  compared  with  other  objects, 
through  the  medium  of  the  visual  organ. 

Sign.  That  by  which  anything  is  represented. 
The  sign   of  addition    (  +  )    represents   convex 


sperical  and  convex  cylindrical  lenses.  The 
sign  of  subtraction  (  —  )  is  used  to  represent 
concave  spherical  and  concave  cylindrical 
lenses. 

Sine.  (L.  sinus  =  sine.)  The  length  of  a  per- 
pendicular drawn  from  one  extremity  of  an  arc 
of  a  circle  to  the  diameter  drawn  through  the 
other  extremity.  Sine  of  an  angle  is  a  circle 
whose  radius  is  unity,  the  sine  of  the  arc  that 
measures  the  angle;  in  a  right-angled  triangle, 
the  side  opposite  the  given  angle  divided  by  the 
hypotenuse.  Versed  sine,  that  part  of  the  diam- 
eter between  the  sine  and  the  arc. 

Sinis'trad.  fGr.  sinister  =  left  +  ad  =  to.)  To  or 
toward  the  left. 

Sinus  (si'-nus).  (L.  "gulf.")  A  hollow  cavity. 
Frontal  Sinus,  one  of  the  two  irregular  cavities 
in  the  frontal  bone  containing  air  and  commu- 
nicating with  the  nose  through  a  funnel-shaped 
passage.  Occipital  Sinus  is  the  smallest  of  the 
cranial  sinuses,  occasionally  there  are  two.  It 
is  situated  in  the  attached  margin  of  the  falx 
cerebelli,  opening  into  the  torcular  Herophili. 
Lateral  Sinus,  two  veins  of  the  dura  running 
along  the  crucial  ridge  of  the  occipital  bone. 
Cavernous  Sinus,  venous  cavities,  starting  be- 
hind the  sphenoidal  fissure,  running  back  on  the 
side  of  the  pituitary  fossa,  and  joining  the  su- 
perior and  inferior  petrosal  sinuses.  Each  cav- 
ernous sinus  receives  anteriorly  the  superior 
ophthalmic  vein  through  the  sphenoidal  fissure. 
on  the  inner  wall  of  each  sinus  is  the  internal 
corotid  artery,  filaments  of  the  corotid  plexus, 
abducent    nerve;    and    on   the    outer    wall,    the 


OPHTHALMIC  DICTIONARY  235 

trochlear,  ophthalmic,  oculo  motor  and  the 
maxillary  division  of  the  trigeminal  nerves. 

Skiascope  (ski'-as-kope).  (Gr.  skia  =  shadow + 
skopeo  ^=  I  examine.)  Better  known  as  the 
retinoscope. 

Skiascopy.  (Gr.  skia  =^  shadow  -f-  skopeo  =  I  ex- 
amine.)    See  Retinoscopy. 

Snellen,  M.  D.,  Prof.  H.  Born  in  Holland.  A  pro- 
fessor of  ophthalmology  occupying  the  chair  at 
the  University  at  Utrecht,  Holland.  A  pupil  of 
Dr.  F.  C.  Bonders,  whom  he  succeeded  in  prac- 
tice and  his  professorship.  He  devised  a  chart 
consisting  of  letters  and  symbols  by  which  the 
subjective  means  of  measuring  the  range  of 
vision  could  be  uniformly  and  scientifically  de- 
termined. It  is  held  by  Snellen  that  in  order  to 
distinguish  one  letter  from  another  the  eye  must 
be  able  to  distinguish  the  spaces  between  the 
lines  which  correspond  to  a  visual  angle  of  1'. 
This  is  true  for  certain  letters,  as,  for  instance, 
to  differentiate  between  O  and  C,  where  the  eye 


Snellen  Chart. 

must  distinguish  the  white  space  which  inter- 
rupts the  circle  in  C.  The  same  is  true  for 
E  and  F,  but  the  principle  is  not  applicable  to 
the  other  letters  of  his  series.    In  a  lecture  on 


refraction  by  Landolt,  we  learn  of  what  great 
advantage  it  is  to  determine  the  visual  aciite- 
ness  and  the  refraction  at  the  same  time.  We 
must  determine  the  refraction  at  such  a  dis- 
tance as  shall  exclude  the  accommodation  as 
much  as  possible.  For  this  a  distance  of  twenty 
feet,  or  six  metres,  is  necessary.  We  therefore 
place  our  test  type  at  20  F,  and  see  what  are  the 
smallest  characters  which  each  eye,  separately, 
can  distinguish.  These  types  are  so  designed 
that  at  the  distance  at  which  they  should  be 
seen  they  each  subtend  an  angle  of  5'  at  the  eye. 
And  when  the  letters  marked  20,  or  6  M,  are 
read  from  20  F,  vision  is  said  to  be  normal,  and 
an  eye  with  normal  vision  can  read  any  of  the 
letters  on  the  chart  at  the  distance  at  which 
they  are  marked. 

Snow-bllndness.  Long  exposure  of  the  eyes  to  the 
glare  from  snow  gives  rise  to  an  acute  conjunc- 
tivitis, attended  with  intense  pain,  photophobia, 
and  occasionally  conjunctival  hemorrhages. 

Socket  (sok'-ket).  (L,  soccus  =  a  show,  a  sock.) 
A  hollow  part  into  which  a  corresponding  part 
fits. 

Spasm.  (L.  spasmus  =  I  draw.)  An  involuntary 
contraction  of  a  muscle.  Spasm  of  accommoda- 
tion is  a  spasmodic  contraction  of  the  ciliary 
muscles,  thus  increasing  the  convexity  of  the 
crystalline  lens  and  making  the  eye  appear  to 
have  a  higher  refractive  power.  There  are  two 
kinds — tonic  and  clonic.  Tonic  s.  is  where  the 
spasm  persists  for  a  considerable  time,  and 
Clonic  s.  is  where  the  muscles  contract  and  re- 
lax intermittently. 


OPHTHALMIC  DICTIONARY  lia7 

Spectacles.  (L.  spectare  ^  to  regard.)  A  pair  of 
lenses  mounted  in  frames  with  temples  attached. 

Spectrum  (spec'-tnim).  White  light  is  composed 
of  all  the  colored  lights  known,  and  when  it  is 
separated  by  a  prism  or  other  means  and 
thrown  on  a  white  screen,  in  an  otherwise  dark 
room,  a  band  of  colors  resembling  a  rainbow 
is  seen.  This  is  called  a  prismatic  or  solar 
spectrum. 

Of  the  seven  primary  colors  which  form  the 
spectrum,  Violet  is  refracted  the  most,  then 
Indigo,  Blue,  Green,  Yellow,  Orange  i',nd  Red 
the  least.  There  are  also  invisible  rays  called 
"ultra'-red,  and  ''ultra"-violet  beyond  its  ap- 
parent boundaries. 

Ocular  Spectrum  color  seen  by  an  eye  where 
none  exists. 

Diffraction  Spectrum  is  a  spectrum  produced 
by  diffraction. 

Chromatic  Spectrum  is  the  visible  colored 
rays  of  the  solar  spectrum,  showing  the  seven 
principal  colors  in  their  order  and  covering  the 
larger  portion  of  the  space  of  the  w^ole  spec- 
trum. 

Sphenoid  (sphe'-noid).  (Gr.  sphen  =  wedge -f 
eidos  =  resemblance.)  Sphenoid  Bone.  A  bone 
situated  at  the  upper  and  back  part  of  the 
orbits  on  the  median  line,  at  the  base  of  the 
cranium.  It  articulates  with  all  the  other  bones 
of  that  cavity,  and  strengthens  their  union. 
When  seen  from  above  it  resembles  a  bat  with 
its  wings  extended. 

Sphere  (sfer).  (3r.  sphaira  =  a  ball.)  A  ball- 
like body. 


Spherical.  Having  the  form  of  a  sphere.  Spherical 
Lens  is  one  the  curved  surface  of  which  is  a 
segment  of  a  sphere  and  is  known  as  a  lens 
with  the  same  refracting  power  in  all  its 
meridians.  There  are  three  ways  to  grind  a 
plus  or  minus  sphere  of  the  same  value; 
namely,  bi-concave,  plano-concave,  periscopic- 
concave,  bi-convex,  plano-convex,  periscopic- 
convex.     See  Lenses. 

Spheroid  (sphe'-roid).  (Gr.  sphaira  =  sphere -h 
eidos  =  resemblance.)  That  which  resembles  a 
sphere  in  shape. 

Spherometer.  (Gr.  sphaira  =  sphere  +  metron  ^ 
measure.)  An  apparatus  for  measuring  the 
curvature  of  a  surface. 

Sphincter  (sphinc'-ter).  (Gr.  sphinkter  =  a  band.) 
A  ring-like  muscle.  The  sphincter  muscle  of 
the  iris  when  contracted  closes  down  the  pupil. 
"When  relaxed  allows  the  pupil  to  become 
dilated. 

Spintherism  (spin'-ther-ism).  (Gr.  spinther  = 
spark.)  That  condition  in  which  the  patient 
complains  of  seeing  star-like  flashes  of  light. 

Squamous  (skwa'-mus).    Scaly. 

Square  (skwar).  (L.  quatuor  =  four.)  (a)  An 
equilateral  rectangle,  (b)  The  second  power  of 
a  number,  (c)  To  raise  a  number  to  the  second 
power. 

Squint.  (Fr.  guigner  to  wink  or  direct  with  one 
eye.)  The  act  of  half  closing  the  eyelids  while 
viewing  an  object.  The  word  squint  is  some- 
times used  to  denote  strabismus. 

Staphyloma  (sta-fy-lo'-mah).  (Gr,  staphyle  =^ 
grape  +  oma  =  tumor.)     A  bulging  of  the  cor- 


on  I'ln  A  LM  1( "   I  >ICTIONAIiY 


230 


nea  or  sclera.  Anterior  s.,  a  bul^inK  forward  of 
the  anterior  portion  of  the  eye.  Posterior  s., 
backward  bulging  of  the  posterior  pole  of  the 
o>  e. 

Stat'ic. .  (Or.  statikos  causing  to  stand.)  Not 
in  motion:  in  a  state  of  rest.  The  static  refrac- 
tion is  the  refraction  of  the  eye  with  the  mus- 
cles of  accommodation  at  rest;  just  the  reverse 
to  dynamic  refraction. 

Steato'sis.  (dr.  stear  (steat)  ==  tallow -f- sufTix 
osis  condition.)  That  condition  in  which  we 
have  fatty  degeneration;  disease  of  the  sebace- 
ous glands. 

Stenopaic  Slit  (sten-o-pa'-ic).  (Gr.  stenos  = 
narrow  -f  ope  =  opening.)  An  accessory  to  be 
found  in  any  complete  trial  case,  and  consists 
of  an  opaque  disc  with  a  slit  about  an  inch  long 


and  one  millimetre  wide.  It  is  used  for  the  pur- 
p().s«'  of  linding  the  principal  meridians  in  cases 
of  regular  astigmatism.  If  vision  is  near  nor- 
mal it  is  best  to  fog  or  blur  it  a  line  or  two  with 
a   plus  sphere,  then   place  the   disc   in   the   trial 


frame  in  front  of  the  eye  we  are  about  to  ex- 
amine, while  the  other  is  covered  by  the  opaque 
disc.  Instruct  the  patient  to  revolve  the  disc  in 
the  trial  frame  while  trying  to  see  the  letters 
on  Snellen's  test  type  at  a  distance  of  twenty 
feet  (never  tlie  astigmatic  wheel)  and  stop  when 
the  best  vision  is  obtained,  thus  locating  the 
principal  meridian  with  least  error.  We  then 
DOte  the  degree  mark  on  the  trial  frame  to 
which  the  slit  is  pointing  and  make  a  right  angle 
cross  on  a  piece  of  paper  showing  this  meridian 
and  the  one  at  right  angles.  We  now  proceed 
to  correct  the  error  by  placing  spheres  over  the 
slit  until  we  find  the  strongest  plus  or  weakest 
minus  that  allows  the  best  vision,  writing  the 
amount  on  the  arm  of  the  cross  corresponding  to 
the  slit.  Then  revolve  the  slit  90°  and  fit  this 
meridian  as  above,  writing  the  amount  on  the 
other  arm  of  the  cross.  From  this  cross  we 
write  the  Rx  without  any  change.  This  will 
represent  the  Ametropia. 

Stereoscope  (ster'-e-o-scope) .  (Gv.  stereos  =  solid 
-5- skopeo  =  I  view.)  An  instrument  composed 
of  two  prisms  arranged  in  such  a  way  that  two 
separate  pictures  of  the  same  kind  may  be  seen 
as  one.  This  instrument  makes  the  picture 
more  natural,  as  the  objects  appear  to  stand 
out. 

Stereoscopic  Vision  (ster-e-o-scop'-ic).  Where  we 
have  equal  vision  with  the  two  eyes  and  the 
objects  appear  to  stand  out  in  solid  form,  and 
are  not  seen  as  flat  pictures. 

Stilling's  Canal.  (Benedict  Stilling,  German  anato- 
mist,  1810-1879.)      A   small   canal   leading   from 


I 


OPHTHALMIC  DICTIONARY  241 

the  optic  disc  through  the  vitreous  humor  to  the 
lens  of  the  eye.    See  Anatomy. 

Stiilicidium  (stil-li-sid'-i-um).  (L.  stilla  =  drop -f- 
cadere  =  to  fall.)  An  overflowing  of  the  tears 
upon  the  check  due  to  a  stricture  of  or  a  nar- 
rowing of  the  nasal  duct.     Same  as  epiphora. 

Stilus  fsti'-lus).  (L.  stilus  =  a  stake.)  A  small 
instrument  made  of  gold  or  silver  used  for 
dilating  the  lacrimal  duct. 

Stoke's  Lenses.  (William  Stokes.  Dublin  physi- 
cian. 1804-1878.)  An  instrument  that  was  used 
in  the  diagnosis  of  astigmatism. 

Stop-needle.  A  needle  with  a  disc  attached  to 
regulate  the  depth  of  penetration. 

Strablsmometer  (strab-is-mom'-e-ter).  (Gr.  stra- 
bismos  +  metron  =  measure.)  An  instrument 
for  measuring  the  degrees  of  strabismus. 

Strabismus  (stra-bis'-mus).  (Gr.  strabismos  = 
distorted.)  (Cross-eyed.)  That  condition  in 
which  the  eyes  are  not  parallel  for  distant 
vision.  The  visual  axis  of  one  eye  only  is  di- 
rected towards  the  object  looked  at;  this  is 
known  as  the  fixing  eye,  while  the  other  is 
known  as  the  deviating  eye.  It  is  caused  by 
anything  which  develops  preponderance  of 
power  in  a  muscle,  either  directly  or  indirectly. 
It  may  be  due  to  an  uncorrected  error  of  re- 
fraction; or  from  anything  which  prevents 
binocular  vision,  such  as  cataract,  corneal  opaci- 
ties, displaced  macula  lutea,  a  short,  long,  or 
paralyzed  muscle.  However,  it  is  well  to  cor- 
rect any  ametropia,  for  when  a  person  has  an 
error  of  refraction  in  one  eye  that  interferes 
with  the  vision  of  its  fellow,  he  will  learn  to 


turn  the  eye  with  the  error  to  one  side.  Alter- 
nating s.,  affecting  both  eyes  equally,  but  not  at 
the  same  time.  Concomitant  s.  is  that  form  of 
strabismus  in  which  one  eye,  although  deviated, 
always    moves    with    the    other,    so    that    the 


One  Eye   turning  in. 


Both  Eyes  turning  in. 


Both  Eyes  turning  out. 


amount  of  deflection  remains  the  same.  Para- 
lytic s.  is  due  to  paralysis  of  one  or  more  of  the 
extrinsic  muscles,  and  the  eye  remains  station- 
ary. Hypermetropia  is  responsible  for  80  per 
cent  of  converging  strabismus  on  account  of 
the    ciliary    muscles    and    the    internal    rectus 


OPHTHALMIC  DICTIONARY  :i43 

muscles   being  supplied  by  one   and   the   same 
nerve. 

When  the  eye  attempts  to  accommodate  in 
order  to  overcome  the  hypermetropia,  the  in- 
ternal rectus  will  contract,  and  if  the  patient 
has  not  the  nerve  energy  to  control  the  external 
rectus,  the  eye  will  turn  in.     See  Heterotropia. 

Strabotomy  (stra-bot'-o-my).  (Gr.  "oblique"  + 
tome=  a  cutting.)  An  operation  calling  for  the 
outting  of  an  ocular  tendon  for  relief  in  cases  of 
strabismus. 

'otrain.  (L.  stringere  =  to  bind.)  Injury  from 
over-use.  Ciliary  s.,  the  result  of  overwork  of 
the  ciliary  muscles  in  hypermetropia  and  some- 
times in  emmetropia.  Muscular  s.,  overwork  of 
the  extrinsic  muscles  as  in  heterophoria. 
Retinal  s.,  fatigue  of  the  retina  caused  by  too 
strong  light  or  from  over-use  in  a  normal  light. 
The  eye  should  be  protected  from  all  direct 
rays  of  light,  as  only  reflected  light  is  neces- 
sary for  vision. 

Stroma  (stro'-ma).  (Gr.  "I  spread  out.")  The 
foundation  tissue  or  support  of  a  formation. 

Stye  ("to  rise")  or  Hordiolum.  A  small  boil  af- 
fecting the  connective  tissue  near  the  edge  of 
the  eyelid,  sometimes  several  appear  at  once, 
or  there  may  be  a  succession  of  them.  They 
cause  swelling  of  the  lid.  In  a  day  or  two  the 
swelling  increases,  with  considerable  pain,  and 
the  skin  over  it  becomes  red,  afterwards  show- 
ing a  yellowish  discoloration  at  the  center  that 
finally  opens  near  the  border  of  the  lid,  with  a 
discharge  of  pus.  After  which  the  inflammatory 
symptoms   abate   and   the   cavity   soon   closes. 


Treatment:  Small  poultices  or  hot  fomenta- 
tions until  pus  forms,  then  open  by  incision 
parallel  to  the  edge  of  the  lid.  General  health 
requires  attention  if  eye  strain  is  not  the  cause. 

Subarach'noid     Space.        (L.     sub  =  under  +  Gr. 
arachne  ^^  cobweb  +  eidos  =  resemblance.) 
That  space  between  the  dura  mater  and  the  pia    . 
mater  which   forms   the   optic   sheath   and   the 
Capsule  of  Tenon. 

Subconjunctival  (sub-con-junc-ti'-val).  That  which 
is  situated  just  beneath  the  conjunctiva. 

Subjective  (sub-jec'-tive).  That  which  pertains 
to,  or  is  perceived  by,  an  individual.  Not  per- 
ceptible to  any  other  person.  It  refers  to  the 
patient  as  he  sees  objects  or  feels  concerning 
his  own  impressions. 

Subla'tio  Ret'inae.  (L.  sublatus  =  taken  away -f 
rete  =  net.)     Detachment  of  the  retina. 

Subluxa'tion.  (L.  sub  =  under  -f  luxare  =  to  dis- 
locate.) Where  the  lens  of  the  eye  is  a  little 
displaced,  subluxation  may  consist  in  the  lens 
being  turned  a  little  obliquely,  so  that  one  end 
of  it  looks  somewhat  forward.  This  condition 
may  be  recognized  from  the  unequal  depth  of 
the  anterior  chamber.  In  cases  of  luxation, 
that  is,  where  the  lens  has  left  its  place  fn  its 
capsule,  so  that  it  partly  covers  the  pupil,  that 
part  of  the  pupil  which  is  a  deep  black  has  no 
lens,  while  the  part  which  contains  the  lens 
would  be  of  a  delicate  gray.  Any  dislocation 
of  the  lens  entails  a  considerable  disturbance  of 
vision.  If  the  lens  still  lies  behind  the  pupil  the 
eye  becomes  very  myopic,  because  the  lens  is  | 
allowed   to  assume  its  maximum  convexity  on   ' 


T^^A 


OPHTHALMIC  DICTIONARY  245 

account  of  separating  from  the  suspensory  liga- 
ments which  keep  it  elongated  when  the  eye  is 
at  rest.  Invariably  any  tear  in  the  suspen- 
sory ligament  results  in  soft  cataract.  Added 
to  this  is  a  considerable  degree  of  astigmatism. 
Dislocations  of  the  lens  usually  entail  second- 
ary consequences  which  may  be  extremely  dis- 
astrous to  the  eye,  but  in  those  cases  in  which 
the  dislocation  entails  no  further  injurious  con- 
sequences than  the  disturbance  of  vision,  the 
treatment  consists  in  prescribing  suitable 
glasses. 

Suborbital  (sub-or'-bit-al).    Beneath  the  orbit. 

Subretinal  (sub-ret'-in-al).  Situated  beneath  the 
retina. 

Subtraction  (sub-trak'-shun).  (L.  sub  =  under -f- 
trahere  =^  draw.)  The  operation  of  finding  the 
difference  between  two  numbers. 

Subvolution  (sub-vo-lu'-shun).  (L.  sub  =  under  + 
volvere  =^  to  turn.)  An  operation  for  the  re- 
moval of  a  pterygium. 

Suction  (suc'-shun).  (L.  sugere  =  to  suck.)  A 
method  by  which  fluid  is  withdrawn. 

Suffusion  (suf-fu'-zhun).  L,  suffundere  =  to  pour 
down.)  State  of  being  blood-shot,  or  of  being- 
moistened.  A  suffusion  of  tears  is  an  excess  of 
the  flow  of  tears. 

Super  Cilia.  fUpper  hairs.)  (L.  super  =  above  -f- 
cilium       eyelash.)     The  eyebrows. 

Superciliary  (su-per-cil'-i-a-ry).  That  which  per- 
tains to  the  eyebrow. 

Supra  Choroidal  Space.  The  space  between  the 
sclerotic  and  choroid. 


Supraduction,  Sursumvergence.  (L.  sursum  =  up- 
ward +  vergere  =  to  bend.  The  act  or  power  of 
turning  one  eye  above  its  fellow. 

Supraorbital  (su-pra-or'-bi-tal).  (L.  supra  =  above 
+  orbita  =  orbit.)     Located  over  the  orbits. 

Supra-orbital  Foramen.  A  small  passage  in  the 
Supra-orbital  Ridge  through  which  passes  the 
supra-orbital  nerve  (a  branch  of  the  fifth) 
artery  and  vein. 

Surface  (ser'-fas).  (L.  superficies  =  the  upper 
face.)   The  bounding  or  limiting  parts  of  a  solid. 

Sursumduction  (sur-sum-duk'-shun),  (L.  sursum 
=  upward  +  ducere  =  to  draw.)  The  act  of 
turning  one  eye  upward  independent  of  its  fel- 
low. The  test  is  made  by  placing  the  base  of 
the  prism  down  until  we  find  the  strongest 
which  the  eyes  can  see  an  object  singly.  It  is 
seldom  more  than  3°. 

Sursumvergence   (sur-sum-vur'-jenz). 
=  upward  +  vergere  =  to    turn.) 
turning  of  the  eye. 

Sursumversion    (sur-sum-vur'-shun). 
=  upward  +  vertere  =  to    turn.) 
turning  the  eyes  upward. 

Suspensory  (sus-pen'-so-ry).     (L.  suspendere 
suspend.)    Serving  to  hold  up  a  part. 

Suspensory  Ligaments.  The  hyaloid  membrane 
forms  the  hyaloid  sac  in  which  the  vitreous 
humor  is  contained.  It  runs  forward  up  over 
the  ciliary  body,  divides  and  forms  the  suspen- 
sory ligaments,  which  are  attached  to  the  lens 
capsule.  C.  B.  Lockwood.  in  a  journal  of  Anat- 
omy and   Physiology,  vol.   XX.,  part  I. — Ed.  of 


(L. 

sursum 

An 

upward 

(L. 

sursum 

The 

act    of 

to 


OPHTHALMIC  DICTIONARY  247 

15th  English  edition,  has  also  described  a  thick- 
ening of  the  lower  part  of  the  Capsule  of  Tenon, 
which  he  has  named  the  suspensory  ligament  of 
the  eye.  It  is  slung  like  a  hammock  below  the 
eyeball,  being  expanded  in  the  center  and  nar- 
row at  its  extremities,  which  are  attached  to 
the  malar  and  lachrymal  bones  respectively. 

Suture  fsu'-ture).  (L.  sutura  =  a  seam.)  The 
serrated  junction  of  the  intracranial  bones. 
Dovetail  joint. 

Sylvius,  Aqueduct  of.  A  passage  from  the  third 
to  the  fourth  ventricle  of  the  brain. 

Symblepharon  (sym-blef'-ar-on).  (Gr.  syn  =  to- 
gether +  blephron  =  eyelid.)  Adhesion  of  the 
lids  to  the  eyeball.  This  develops  whenever 
two  opposed  spots  of  the  conjunctiva  of  the  lid 
and  of  the  eyeball  have  raw  surfaces  which 
come  into  contact  with  each  other,  and  in  con- 
sequence become  adherent.  Causes  which  can 
give  rise  to  the  formation  of  raw  surfaces  upon 
the  conjunctiva  are  burns  by  the  action  of  heat, 
burns  from  caustic  substances,  diphtheria,  oper- 
ations, ulcers  of  all  kinds,  etc. 

Sympathetic  Ophthalmitis  (sym-pa-thet'-ik  of-thal- 
mi'-tis).  (Gr.  syn  =  with  +  pathos  =  suffering 
+  ophthalmos  =  eye  -f  itis.)  An  inflammatory 
condition  of  the  iris  and  ciliary  body,  which  is 
developed  through  an  injury  or  disease  of  the 
opposite  eye. 

Symptoms.  (Gr.  syn  =  with  +  ptoma  =  I  fall.)  A 
perceptible  change  which  indicates  disease,  or 
that  which  indicates  the  existence  of  something 
else.     See  Objective  and  Subjective  Symptoms. 

Synchysis  (syn'-chy-sis).     (Gr.  confusion.)     Lique- 


faction  of  the  vitreous.  When  observing  opaci- 
ties of  the  vitreous  with  the  ophthalmoscope, 
we  see  that  most  of  them  float  about  freely  in 
the  vitreous.  From  this  we  would  assume  that 
the  framework  of  the  vitreous  must  have  been 
destroyed,  so  that  this  body  Itself  is  converted 
into  a  perfectly  liquid  mass. 

Syndesmi'tis.  (Gr.  syndesmos  =  ligament  +  itis 
=  inflammation.)  That  condition  in  which 
there  is  inflammation  of  a  ligament  or  of  the 
conjunctiva. 

Synechia  (syn-e'-chi-ah).  (Gr.  synecheia  =  con- 
tinuous.) Adhesion,  as  of  the  iris  to  the  lens 
or  cornea.  Posterior  s.,  adhesions  of  the  iris  to 
the  lens  capsule.  Anterior  s.,  adhesions  of  the 
iris  to  the  cornea. 

Synizesis  (sin-iz-e'-sis).  (Gr.  "a  falling  in.")  Con- 
traction of  the  pupil  of  the  eye. 

Synophthalmus  (syn-of-thal'-mus).  (Gr.  syn  =  to- 
gether +  ophthalmos  =  eye.)  A  one-eyed  mon- 
ster. 

Syntropic  (sin-trop'-ik).  (Gr.  syn  =  together  + 
tropikos  =  turning.)  Turned  in  the  same  direc- 
tion. 

System.  (Gr.  systema  =  to  place  together.)  A 
bodily  organism.  An  assemblage  of  parts  or 
organs  which  unite  in  a  common  function. 


JL  •    An  abbreviation  for  tension  or  temperature. 

Tangent  (tan'-gent).  (L.  tangere  =  to  touch.) 
Touching  at  a  single  point;  specifically  meeting 
a  curve  or  surface  at  a  point  and  having  at  that 


OPHTHAI.MIC  DICTIONARY  249 

-point  the  same  direction  as  the  curve  or  sur- 
face— said  of  a  straight  line,  curve  or  surface; 
as.  a  line  tangent  to  a  curve;  a  curve  tangent  to 
a  surface;  tangent  surfaces.  Tangent  plane  is 
a  plane  which  touches  a  surface  in  a  point  or 
line. 

Tapetum  (ta-pe'-tum).  (L.  "a  carpet.")  The 
luminosity  seen  in  the  eyes  of  many  beasts.  A 
lustrous,  greenish  membrane  seen  in  the  eyes 
of  cats  and  many  animals  that  require  night 
vision. 

Tarsal  Cartilages  ftar'-sal  kar'-til-aj-es).  (Gr. 
tarsos  =  a  wicker  work  frame  +  cartilago  == 
gristle.)  That  which  forms  the  tough  skeleton 
layer  of  the  eyelids,  giving  them  rigidity  of 
form  and  affording  them  firm  support.  The 
shape  is  like  that  of  the  lids  being  fastened 
around  the  edge  of  the  orbit.  The  tarsus  of  the 
upper  lid  is  broader  than  that  of  the  lower. 

Tarsitis  (tars-i'-tis).  (Gr.  tarsos  =  a  wicker  work 
frame  -f-  itis  =  inflammation.)  An  inflammation 
involving  the  tarsal  cartilages. 

Tarsoplasty  (tar'-so-plas-ty).  (Gr.  tarsos  +  plasso 
=  I  form.)     Plastic  surgery  of  the  tarsus. 

Tarsorrhaphy  (tar-sor'-a-fe).  (Gr.  tarsos  +  rhaphe 
=  a  stitching.)     An  operation  upon  the  eyelids. 

Tarsotomy  (tar-sot'-o-my).  (Gr.  tarsos -j- tome  = 
incision.)  A  surgical  operation  which  involves 
the  cutting  of  the  tarsal  cartilages. 

Tarsus  (tar'-sus).  (Gr.  tarsos  =  a  wicker  work 
frame.)  That  which  forms  the  skeleton  of  the 
eyelid,  giving  it  rigidity  of  form  and  affording  it 
firm  support.  The  tarsus  of  the  upper  lid  is 
broader  than  that  of  the  lower 


Tears.  The  watery  secretion  of  the  lacrimal 
glands. 

Teichopsia  (tei-kop'-si-ah).  (Gr.  teichos  =  wall + 
opsis  =  vision).  A  luminous  appearance  before 
the  eyes,  with  a  zigzag,  wall-like  outline. 

Telangiectasis  (tel-an-je-ek'-ta-sis).  (Gr.  telos  = 
end  ==  angeion  =  vessel  +  ektasis  =  a  stretch- 
ing out.)     Dilatation  of  capillaries. 

Tendency  (tend'-en-cy).  A  disposition  on  the  part 
of  a  muscle  to  incline  toward  certain  directions. 

Tendon  (ten'-don).  (L.  tendo  =  I  stretch.)  The 
fibrous  cords  by  which  the  muscles  are 
attached. 

Tendons.  (Sinew.)  White,  glistening,  fibrous 
cords,  varying  in  length  and  thickness,  some- 
times round,  sometimes  flattened,  of  consider- 
able strength  and  devoid  of  elasticity.  Apon- 
euroses are  flattened  or  ribbon-shaped  tendons. 
They  are  without  nerves  and  have  very  few 
blood-vessels.  Tendons  pass  through  all  mus- 
cles and  form  their  attachment  at  each  end. 

Tendon  of  Lockwood  gives  origin  to  the 
Superior  Internal  and  upper  head  of  the  Ex- 
ternal recti  muscles.  It  is  part  of  the  ligament 
of  Zinn. 

Tenonitis  (ten-on-i'-tis).  (Gr.  tenon  =  tendon  + 
itis.)     Inflammation  of  the  Capsule  of  Teno^^. 

Tenon's  Capsule.  (Jacques  Tenon,  French  anat- 
omist, 1724-1816.)  (Tunica  vaginalis  oculi.)  The 
cup-like  thin  membranes  which  envelop  the  eye- 
ball, covering  the  sclera  from  the  optic  nerve  to 
the  ciliary  region,  where  it  joins  the  ocular  sub- 
conjunctival tissue.    The  space  within  the  orbit 


OPHTHALMIC  DICTIONARY  251 

which  is  not  occupied  by  the  eyeball,  its  mus- 
cles, nerves,  vessels  or  other  parts  belonging  to 
it  is  completely  filled  with  soft,  fat  and  deli- 
cate, elastic  connective  tissue.  In  various  places 
this  tissue  is  condensed  into  two  layers  of  con- 
siderable strength.  One  layer  investing  the 
sclera  of  the  eyeball  and  the  other  lining  the 
cushion  of  fat  in  which  the  eyeball  rests.  These 
two  layers  lined  with  flattened  endothelial  cells 
encloses  a  lymph  space  which  communicates 
with  the  subdural  and  subarachnoid  lymph 
spaces  of  the  optic  sheath.  They  are  traversed 
by  delicate  bands  of  connective,  elastic  tissue, 
thus  forming  a  flexible  socket,  in  which  the  eye- 
ball rotates  by  means  of  its  muscles.  This  cap- 
sule is  perforated  by  the  ocular  muscles  and  is 
reflected  back  on  each  as  a  tubular  sheath. 
These  two  layers  are  sometimes  referred  to  as 
the  dura  mater  and  pia  mater,  owing  to  their 
connection  through  the  optic  sheath,  with  the 
dura  and  pia  mater  which  lines  the  skull. 

Tenotomy  (ten-ot'-om-e).  (Gr.  tenon  =  tendon + 
tome  =  incision.)  An  operation  for  cutting  or 
dividing  the  tendon  of  a  muscle. 

Tension  (ten'-shun).  (L.  tendere  =  to  stretch.) 
The  condition  of  being  stretched  or  tense. 

Tensor-tarsi  Muscle  (ten-sor-tar'-si).  A  very  small 
muscle  located  at  the  inner  canthus  of  the  eye. 
It  takes  its  origin  at  the  crest  of  the  lacrimal 
bone,  and  is  inserted  into  the  tarsal  cartilage  of 
the  eye-lids.  It  is  supplied  by  the  facial  nerve. 
Its  use  is  to  compress  the  puncta  and  lacrimal 
sac. 

Test.     (L.  testis  =  witness.)     An  examination  or 


trial.     T.  types,   letters  of  various  shapes  and 
sizes  used  in  testing  visual  power. 
Tetranopsia  (tet-ran-op'-si-a).     (Gr.  tetra  =  four + 
an  -   away  +  opsis  —  vision.)       Obliteration    of 
one-fourth  of  the  visual  field. 

Thermometer  (ther-mom'-e-ter).  (Gr.  therme  = 
heat  +  metron  ^^  measure.)  An  instrument  by 
which  temperature  is  measured. 

Thalamus  (thal'-a-mus).  (A  room;  a  bed.)  The 
place  in  which  a  nerve  originates,  Optic  Thal- 
amus. A  mass  of  nerve  matter  on  both  sides  of 
the  third  ventricle  of  the  brain. 

Thrombosis  (throm-bo'-sis).  (Gr.  thrombosis  =  a 
curdling,  a  clot.)  The  formation  of  a  blood-clot 
in  a  vessel  at  the  point  of  obstruction. 

Thyroid  (thi'-roid).  (Gr.  thyreos  =  an  oblong 
shield  +  eidos  =  form.)  Shield-shaped.  T.  Gland 
is  a  vascular  body  situated  at  the  front  and 
sides  of  the  neck,  and  extending  upwards  upon 
each  side  of  the  larynx.  It  is  a  single  gland, 
varying  greatly  in  size  in  different  individuals. 

Tinea  Tarsi.  Blepharitis  marginalis.  See  Bleph- 
aritis. 

Tobacco  Amaurosis.  (Gr.  amauros  —  obscure.)  A 
dimness  of  vision  caused  by  the  excessive  use 
of  tobacco,  which  acts  directly  upon  the  nervous 
system.  The  reduction  in  the  visual  acuity  is 
almost  always  the  same  in  both  eyes.  Treat- 
ment consists,  first  of  all,  in  abstinence  from 
tobacco,  and  it  is  probable  that  in  light  cases 
this  alone  is  sufficient  to  effect  a  cure. 

Tonic  Spasm.  (Gr.  tone  +  "to  draw.")  A  con- 
tinuous  involuntary   contraction   of   the   ciliary 


OI'IITIIALMIC  DICTIONARY  253 

muscles.      This    condition    may    exist    in    any 
muscle. 

Tonometer  ( to-nom'-e-ter).  (Gr.  tones  —  tone  4- 
metron  measure.)  An  instrument  for  meas- 
uring the  tension  of  the  eyeball. 

Tonic  Lens.  A  lens  with  a  sphere  and  a  cylinder 
on  the  same  side,  usually  periscopic  in  shape. 
See  Lens. 

Torsion  (tor'-shun).  (L.  torquere  =  to  twist.)  A 
twisting. 

Toxic  Amblyopia.  (Gr.  toxikon  =  poison.)  Am- 
blyopia caused  by  a  poison,  a  common  cause 
being  excessive  use  of  tobacco  or  liquor  or  both. 

Trachoma  (tra-ko'-mah).  (Gr.  trachys  ^  rough.) 
Granular  conjunctivitis.  Characterized  by 
slowly  progressive  changes  in  the  conjunctiva 
of  the  eyelids,  in  consequence  of  which  this 
membrane  becomes  thickened,  vascular,  and 
roughened  by  firm,  round  elevations,  instead  of 
being  pale,  thin  and  smooth.  Granular  disease 
is  very  important,  because  it  greatly  increases 
the  susceptibility  of  the  conjunctiva  to  take  on 
acute  inflammation  and  to  produce  contagious 
discharge.  It  often  gives  rise  to  deformities  of 
the  lid  and  to  serious  damage  of  the  cornea. 
The  conditions  which  favor  the  development 
and  spread  of  trachoma  are  unclean  and  over- 
crowded surroundings  in  which  ventilation  is 
neglected,  and  the  locality  is  damp.  The  disease 
is  common  among  school  children  who  are 
poorly  nourished. 

Tract.    See  Optic  Tract. 

Transection    (tran  sek'-shun).     (L.  trans -- across 


-f  sectio;    secare  =  tc   cut.)      A   section   made 
across  a  long  axis. 

Transillumination  (trans-il-lu-min-a'-shun).  (L. 
trans  =  through  +  illuminare  =  to  light  up.) 
The  inspection  of  the  interior  of  an  organ  by 
means  of  a  strong  light. 

Transit.  (L.  trans  =  through.)  A  passing  across. 
A  term  used  in  retinoscopy  to  indicate  move- 
ment of  the  light  area. 

Transi'tional  Zone.  The  posterior  part  of  the  lens 
sac  during  the  stage  of  growth. 

Translu'cent.  (L.  trans  =  through  +  lucere  =  to 
shine.)  The  quality  of  transmitting  rays  of  light 
without  the  object  being  distinctly  seen. 
(Frosted  glass.) 

Transparent.  (L.  trans  =  through  +  parere  =  to 
appear.)  Having  the  property  of  being  clearly 
seen  through. 

Transposition  (trans-po-si'-shun).  (L.  trans  = 
across  +  ponere  =  to  place.)  Changing  the 
form  of  an  optical  prescription  without  changing 
its  optical  value.  To  transpose  a  lens  is  to 
change  its  curves  without  changing  its  refrac- 
tive value. 

To  transpose  an  optical  prescription  is  to 
change  the  form  or  shape  of  the  lens  without 
changing  its  optical  value,  periscopic  effect  be- 
ing the  prime  and  important  feature  in  most 
instances.  The  term  periscopic  is  applied  to 
lenses  having  concavo-convex  surfaces,  which 
enable  the  eye  to  view  with  equal  likeness  on 
all  sides.  When  lenses  are  not  of  this  descrip- 
tion the  desired  result  may  be  obtained  by  the 
following  rules: 


OPHTHALMIC  DICTIONARY  255 

When  the  sign  of  the  sphere  and  cylinder  are 
alike  (i.  e.,  both  plus  or  both  minus)  add  them 
together  for  the  new  sphere,  prefixing  the  same 
sign. 

When  the  sign  of  the  sphere  and  cylinder  are 
different  (i.  e.,  one  plus  and  the  other  minus) 
subtract  for  the  new  sphere,  prefixing  the  sign 
of  the  larger  number. 

Always  change  the  sign  of  the  cylinder  to  the 
opposite,  but  do  not  change  its  value. 

Always  change  the  axis  to  right  angle  (i.  e., 
inove  it  90°). 

For  transposition  of  simple  cylinders,  use  the 
lollowing  rule:  Use  the  numerical  value  of 
your  cylinder  for  the  new  sphere,  prefixing  the 
same  sign,  and  for  the  new  cylinder  use  the 
same  value  as  the  original,  but  prefix  the  oppo- 
site sign  and  change  the  axis  to  right  angle. 

To  co-nvert  cross  cylinders  into  sphero-cylin- 
ders,  apply  the  fpllowing  rule:  Use  the  smaller 
number  for  your  sphere  (if  the  numbers  are 
alike,  take  either  one,  keeping  its  own  sign), 
and  when  the  signs  of  the  cylinders  are  alike 
(i.  e.,  both  plus  or  both  minus)  subtract  them 
for  your  cylinder,  prefixing  the  same  sign. 
When  the  signs  are  unlike  (i.  e.,  one  plus  and 
the  other  minus)  add  them  for  your  cylinder, 
prefixing  the  sign  of  the  remaining  cylinder, 
and  also  its  axis. 

If,  after  transposing  cross  cylinders,  your  pre- 
scription is  not  periscopic,  make  it  so  by  trans- 
posing again  by  one  of  above  rules. 

Below  find  a  few  examples  in  transposition, 
with  their  ansvvers: 


Example,  +  3  sph.  3    —  2  cyl.  ax.  60. 

Answer,     -}-  1  sph.  ^    +  2  cyl.  ax.  150. 

Example,  +  2  sph.  3     +2  cyl.  ax.    90.    . 

Answer,     +  4  sph.  3    —  2  cyl.  ax.  180. 

Example,  +  4  cyl.  ax.  45  3   -f  2  cyl.  ax.  135. 

Answer,     +  2  sph.  3    +2  cyl.  ax.    45. 

Example,  —  3  cyl.  ax.  20  3    +  3  cyl.  ax.  110. 

Answer,    —  3  sph.  3+6  cyl.  ax.  110. 

Example,  +  1  cyl.  ax.  60. 

Answer,     -f  1  sph.  3    —  1  cyl.  ax.  150. 

Writing  a  prescription  from  a  cross  is  not 
transposing.  We  must  first  have  a  written  pre- 
scription before  it  can  be  transposed. 

In  order  to  give  the  patient  glasses  which 
give  them  the  best  possible  results,  it  will  be 
necessary  to  know  how  to  build  lenses  of  dif- 
ferent shapes,  for  instance: 

Biconvex,  biconcave,  piano  convex,  piano  con- 
cave, periscopic  and  toric. 

Lenses  have  two  kinds  of  power,  minus  and 
plus — the  former  being  thinner  in  the  center 
and  the  latter  thinner  at  the  edge.  These  lenses 
can  be  made  up  as  a  sphere  or  cylinder. 

A  sphere  is  a  lens  with  the  same  power  in 
all  its  meridians. 


180 


Cut  sliowfng  how  the   nieiidians  of  an  eye  are  numbered 
from  right  to  left. 


OPHTHALMIC  DICTIONARY 


257 


A  meridian  is  any  straight  line  drawn  from 
edge  to  edge  over  its  optical  center. 

The  optical  center  being  a  point  in  line  with 
the  thickest  part  of  a  plus  and  the  thinnest 
part  of  a  minus  lens. 

A  cylinder  is  a  lens  with  power  in  all  merid- 
ians but  one,  this  one,  having  no  power  and  is 
called  its  axis.  The  full  power  of  a  cylinder  is 
always  found  at  right  angles  to  its  axis. 

In  the  following  diagram  we  will  use  a  plus 
four  dioptry  sphere  and  plus  four  cylinder  for 
example: 


Notice  that  the  power  is  the  same  in  all 
meridians  of  a  sphere,  while  those  of  a  cylinder 
vary  in  power. 

An  optical  prescription  is  nothing  more  than 
an  order  for  a  lens  of  a  given  power  and  shape, 
and  when  it  is  transposed,  the  shape  is  changed 
but  not  its  optical  value  (or  power) ;  for  in- 
stance, we  take  the  following  prescription: 

+  4  sph.  3+4  cyl.  ax.  180. 
which  reads  plus  four  sphere  combined  with  a 
plus  four  cylinder,  axis  180.  The  optician,  on 
receiving  this  prescription,  will  grind  the  plus 
four  sphere  on  one  side  of  the  lens  and  a  plus 
four  cvlinder  on   the  other  and   cut    it  out,   so 


that  the  axis  of  the  cylinder  will  be  at  180". 
This  lens  being  plus  on  both  sides  is  known  as 
a  biconvex  lens. 


+  3. 


In  this  example  we  have  the  sphere  and  cylin- 
der separated  and  together,  showing  their  com- 
bined powers  and  also  their  appearance  from 
the  side.  It  should  be  noted  that  the  sphere 
does  not  change  its  value  under  the  axis  of  the 
cylinder,  thus  forming  one  of  its  principal 
meridians. 

In  order  to  change  the  shape  of  this  lens  we 
must  apply  the  following  rule: 

"When  the  signs  of  the  sphere  and  cylinder 
are  alike,  that  is,  both  plus  or  both  minus,  add 
the  values  together  for  your  new  sphere  which 
would  be  plus  eight,  then  change  the  sign  of 
your  cylinder,  which  makes  it  minus,  but  do  not 
change  its  value.    Change  its  axis  90°,  taking  90 


OPHTHALMIC  DICTIONARY 


259 


from  180  leaves  90,  thus  +  4  sph.  3+4  cyl.  ax. 
180  transposed  gives  you  +  8.  sph.  3  —  4.  cyl. 
ax.  90°.  ^ 

In  the  latter  prescription  you  have  what  is 
known  as  a  periscopic  lens,  one  side  plus  and 
the  other  side  minus. 

■i-8  ^ 


This  shape  lens  is  much  preferred  by  the 
Refractionist  of  today  on  account  of  its  appear- 
ance and  comfort  to  the  patient. 

Trapezoid  (tra-pe'-zoid).  (Gr.  trapeza  =  table  + 
eidos  =  form.)  A  quadrilateral  having  two 
parallel  sides. 

Traumatic  (trau-mat'-ik).  Of,  caused  by.  or  per- 
taining to,  an  injury. 

Trembling  Eyes.    See  Nystagmus. 

Trial  Case  (and  how  to  use  it).  The  ordinary 
trial  case  contains  about  thirty  pairs  of  convex 
and  the  same  number  of  concave  spherical 
lenses,  ranging  from  0.12-D.  up  to  20-Dioptries ; 


twenty  pairs  of  convex  and  the  same  number 
of  concave  cylindrical  lenses  ranging  from 
0.12-D,  up  to  6-Dioptry;  at  least  ten  prisms  from 
1  to  10°;  a  plain  red  tinted  glass;  some  shades 
of  smoked  glasses;  an  opaque  disc;  stenopaic 
slit;  pinhole  disc;  a  ground  glass  disc;  a  Mad- 
dox  rod,  or  double  prism,  and  a  retinoscope; 
two  trial  frames,  one  having  three  cells  to  be 


Trial  Case. 


used  in  fitting,  the  other  two  cells,  so  that  we 
may  allow  a  patient  to  wear  his  correction  for 
a  short  time  and  still  have  one  to  use.  The 
patient  is  seated  20  feet  from  the  test  card, 
which  must  be  well  illuminated,  and  shades 
arranged  so  that  the  light  will  throw  no  direct 
rays  on  the  patient's  face.  Place  a  small  table 
holding  your  trial  case  on  the  patient's  right 
hand  side;  seat  yourself  at  the  table  with  your 
back  to  the  reading  chart.  Now  you  will  find 
yourself  in  a  very  easy  position  to  change  the 
lenses.  The  trial  frame  is  placed  upon  the  pa- 
tient's face  and  adjusted  so  that  he  will  look 


OPHTHALMIC  DICTIONARY  2«1 

through  the  center  of  the  lenses,  having  the 
frame  as  near  the  face  as  possible.  Now  you 
are  in  a  position  to  begin  testing.  First  place 
the  opaque  disc  over  the  left  eye,  always  making 
it  a  rule  to  test  the  right  eye  first,  as  you  will 
tind  all  prescription  blanks  made  out  in  this 
way.  Now  instruct  your  patient  to  read  the 
smallest  line  of  letters  that  he  can  see  with  the 
naked  eye.  We  will  say  in  this  case  he  read  the 
line  marked  60.  As  he  is  seated  20  feet  from 
the  chart,  vision  with  the  naked  eye  is  20/60. 
You  must  always  remember  what  the  vision 
with  the  naked  eye  is,  so  that  you  will  be  able 
to  judge  whether  or  not  the  vision  is  improved 
with  the  correction.  Now  take  a  plus  sphere 
from  the  trial  case,  say  plus  .50-D.,  place  it  be- 
fore the  right  eye,  asking  the  patient  to  again 
read  the  smallest  type  that  he  can  see  clearly. 
Should  the  patient  not  read  as  well,  the  case 
may  be  one  of  emmetropia,  myopia,  or  astig- 
matism; but,  on  the  other  hand,  if  he  reads 
just  the  same  as  before,  or  a  line  better,  it  is 
a  case  of  hypermetropia,  and  we  will  now  pro- 
ceed to  work  out  a  case  of  each  kind. 

Hypermetropia.  In  this  case  we  will  say  he 
read  line  numbered  50.  Then  his  vision  will  be 
20/50.  Now  we  place  before  this  right  eye  a 
plus  ..jO  sphere,  and  if  the  patient  reads  the 
same  or  a  line  better,  it  is  surely  a  case  of 
hypermetropia.  Now,  as  a  plus  lens  will  always 
relax  accommodation,  and  we  do  not  want  any 
eye  to  accommodate  for  20  feet,  or  farther,  we 
will  add  more  plus  in  the  following  manner: 
take  a  plus  1  sphere  and  place  it  in  the  second 
cell  of  your  trial  frame,  then  withdraw  the  plus 


.50.  In  this  way  the  eye  will  not  be  left  uncov- 
ered; again  ask  the  patient  to  read,  and  should 
he  read  as  well  as  before  we  will  increase  the 
plus  sphere  until  the  smallest  line  that  he  reads 
becomes  blurred,  then  we  will  know  that  he  has 
relaxed  all  the  accommodation  he  had  in  use: 
that  being  the  object  of  the  fogging  system. 
Then  draw  the  patient's  attention  to  astigmatic 


/SO' 


=  USO' 


Astigmatic   WheeL 


wheel,  asking  him,  'are  all  the  spokes  in  the 
wheel  equally  clear  and  of  the  same  density?" 
If  there  is  no  astigmatism  the  patient  will  see 
the  wheel  uniformly.  In  that  case  we  would 
ask  him  to  again  look  at  the  reading  chart,  and 
gradually  reduce  the  strength  of  the  plus 
sphere,  until  we  find  the  strongest  that  will 
allow  the  best  vision.  This  will  be  his  correc- 
tion. On  the  other  hand,  had  the  patient  told 
you  that  the  wheel  did  not  look  uniform,  but 
that  one  or  more  of  the  spokes  were  much 
darker,  it  would  indicate  astigmatism,  and  we 
would  ask  the  patient  which  spoke  appeared  the 
most  clearly.  Now,  suppose  he  says  "it  is  the 
vertical,"  or  the  spoke  running  from  12  to  6, 
then  as  we  wish  to  know  if  the  patient  sees  the 


OPHTHALMIC  DICTIONARY  263 

spoke  quite  clearly,  we  will  ask  him  to  count 
the  lines  in  the  spoke.  Should  he  count  the 
right  number  we  will  consider  he  is  seeing  it 
clearly,  and  to  make  sure  that  he  is  not  still 
accommodating  before  we  correct  the  astig- 
matism, we  will  increase  the  plus  sphere  (al- 
ready in  the  trial  frame)  until  we  just  about 
blur  all  the  spokes  in  the  wheel;  then  reduce 
your  sphere  a  quarter  D.  at  a  time,  at  the  same 
time  asking  the  patient  to  inform  you  when  one 
of  the  spokes  comes  out  clearly,  and  he  can  count 
the  lines.  Whatever  plus  sphere  you  have  in 
the  frame  at  this  time,  place  in  the  cell  nearest 
the  eye;  or,  a  better  way  would  be  to  place  a 
plus  sphere  of  the  same  strength  as  the  one 
already  in  the  frame  in  the  cell  nearest  the  eye 
before  removing  the  one  in  front.  In  this  way 
you  will  move  the  lens  in  the  frame  without 
exposing  the  naked  eye.  It  will  then  be  out  of 
the  way  while  using  the  cylinder.  Now  take 
from  your  trial  case  the  weakest  minus  cylinder 
and  place  it  in  the  trial  frame  with  the  axis  at 
right  angles  to  the  plainest  spoke  seen.  Should 
this  fail  to  make  the  wheel  look  uniform,  in- 
crease the  strength  of  your  cylinder  until  you 
find  the  weakest  that  will  make  the  wheel  look 
equal  in  density  in  all  its  spokes.  When  you 
have  done  this,  draw  the  patient's  attention  to 
the  reading  chart,  and  gradually  reduce  the 
strength  of  your  plus  sphere  while  it  improves 
the  distant  vision.  In  other  words,  the  strong- 
est plus  sphere  combined  with  the  weakest 
minus  cylinder  that  corrected  the  astigmatism 
is  the  patient's  correction  for  constant  use. 
Myopia.     Seat  the  patient  as  in  the  previous 


case.  Cover  the  left  eye  with  the  opaque  disc, 
ask  him  to  read  the  smallest  type  he  can  with 
the  naked  eye,  record  this  vision  to  compare  it 
with  the  final  correction.  Now  place  a  plus  .50 
in  the  trial  frame,  and  if  the  patient  is  myopic 
he  will  say,  "I  cannot  see  so  well,"  or  in  other 
words,  will  not  be  able  to  read  the  same  line  as 
before.  Then  draw  his  attention  to  the  astig- 
matic wheel  and  say,  "can  you  see  the  spokes 
in  the  wheel,  and  do  they  look  equally  clear?" 
If  he  cannot  see  any  of  the  spokes  clearly 
enough  to  count  the  lines,  remove  a  quarter  D. 
of  the  plus  sphere.  If  with  this  he  fails  to  see 
any  of  the  spokes  clearly,  remove  the  other 
quarter  from  the  trial  frame.  If  none  of  the 
spokes  are  yet  clear,  begin  with  the  weakest 
minus  sphere  and  gradually  increase  same  a 
quarter  D.  at  a  time  until  one  or  more  spokes 
come  up  clearly.  If  they  all  appear  clear  at  the 
same  time  there  is  no  astigmatism,  and  we  turn 
to  the  reading  chart  and  give  him  the  weakest 
minus  sphere  that  will  allow  him  to  read  the 
best.  This  would  be  his  correction.  On  the 
other  hand,  if  there  is  astigmatism,  the  wheel 
will  not  come  up  equally  clear,  but  some  spokes 
will  be  plainer  than  others.  The  main  point  is 
not  to  increase  the  minus  sphere  after  one  or 
more  spokes  appear  clearly;  for  instance,  wie 
will  say  we  have  on  a  minus  1  sphere  and  the 
patient  tells  us  that  he  cannot  count  any  lines 
in  any  of  the  spokes  as  yet.  We  add  to  this 
sphere  a  minus  .25,  which  will  make  it  minus 
1.25,  and  if  he  says  "Now  I  can  see  one  spoke 
clearly,"  and  it  runs  from  12  to  6.  this  is  the 
time  to  begin  with  the  weakest  minus  cylinder. 


OPHTHALMIC  DICTIONARY  265 

placing  the  axis  at  right  angles  to  the  plain 
spoke,  increasing  its  strength  until  you  find  the 
weakest  that  makes  the  wheel  look  uniform  in 
density.  In  this  case  we  will  say  that  it  re- 
quired a  minus  .75  cylinder,  that  cylinder  com- 
bined with  the  sphere  already  in  the  frame  will 
be  the  correction,  which  will  read  as  follows: 
—  1.25  sph.Q— -75  cyl.  ax.  180. 

Triangfe  (tri'-ang-gl).  (L.  tres  =  three  -f  angulus 
=  angle.)     A  three-sided  plane  figure. 

Trichiasis  (trick-i'-a-sis).  (Gr.  thrix  =  hair.)  That 
condition  where  the  eyelashes,  instead  of  ex- 
tending forward,  are  directed  more  or  less  back- 
ward, so  as  to  come  in  contact  with  the  cornea. 
Trichiasis  causes  a  continual  irritation  of  the 
eyeball,  due  to  the  action  of  the  cilia  (eye- 
lashes) ;  there  is  photophobia,  lachrymation, 
and  a  constant  sense  of  a  foreign  body  in  the 
eye.  The  cornea  itself  suffers  considerable 
injury. 

Trichitis  (trick-i'-tis).  (Gr.  thrix  =  hair  +  itis  = 
inflammation.)  Inflammation  of  the  root  of  the 
eyelashes. 

Trichosis  (tri-ko'-sis).  (Gr.  thrix  =  hair.)  A  dis- 
ease of  the  hair.     See  Trichiasis. 

Trichroic  (tri-kro'-lk).  (Gr.  trichroos  =  three  col- 
ored.) That  which  exhibits  three  different 
colors  in  three  dilTerent  positions. 

Trichromatic  (tri-kro-mat'-ik).  (Gr.  tri  =  three 
^- chroma  =  color.)  That  which  has  three 
colors. 

Trigeminus  (trl-jem'-in-us).  (L.  tri  =  three -f 
geniinus  =  double.)  T.  Nerve,  also  known  as  the 
fifth,  or  trifacial,  is  the  largest  cranial  nerve. 


It  has  two  roots,  motor  and  sensor;  it  is  the 
sensory  nerve  of  the  head  and  face  and  motor 
nerve  of  the  muscles  of  mastication.  It  is  a 
branch  of  this  nerve  that  forms  the  ophthalmic. 
(See  Nerve.) 

Trigonometry  (trig-o-nom'-e-try).  (Gr,  triangle  -i- 
metry.)  That  branch  of  mathematics  which 
treats  of  the  relations  of  the  sides  and  angles 
of  triangles  with  the  methods  of  deducing  from 
certain  given  parts  other  required  parts  and 
also  of  the  general  relations  which  exist  be- 
tween the  trigonometrical  functions  of  arcs  or 
angles.  Plane  trigonometry  and  spherical 
trigonometry  are  those  branches  of  trigonometry 
in  which  its  principles  are  applied  to  plane 
triangles  and  spherical. 

Triplet.  (Gr.  tri  =  three.)  A  combination  of 
three  lenses. 

Triplopia.  (Gr.  triploos  =  triple  +  ops  =  eye.)  A 
visual  defect  in  which  three  images  are  seen 
of  the  one  object. 

Trochlea  (troch'-le-ah).  (L.  pulley.)  A  pulley- 
shaped  part,  such  as  that  through  which  the 
superior  oblique  muscle  passes. 

Trochlearis  (troch-le-a'-ris).  That  which  refers  to 
the  superior  oblique  muscle. 

Tropom'eter.  (Gr.  trope  =  a  turning  -f  metron  =^ 
measure.)  An  instrument  for  measuring  the 
movements  of  the  eye. 

Tumor  (tu'mor).  (L.  tumere  =  to  swell.)  A 
swelling.  A  growth  of  new  tissue,  differing  in 
structure  from  the  part  on  which  it  grows,  not 
the  result  of  inflammation. 


OPHTHALMIC  DICTIONARY  267 

Tunic.  (L.  tunica  =  coat.)  A  name  given  to  dif- 
ferent membranes,  which  envelop  organs;  the 
eye  has  three  tunics  from  without  inward;  first 
the  sclerotic  and  cornea;  second,  choroid,  cil- 
iary body  and  iris  combined;  third,  the  retina 
which  is  the  only  one  sensitive  to  light. 

Tunica.  Same  as  tunic.  T.  adnata,  that  portion  of 
the  conjunctiva  which  comes  in  contact  with 
the  eyeball. 

Tutam'ina  Oculi.  (L.  tutamen  =  a  protection.) 
The  protecting  appendages  of  the  eye,  such  as 
the  eyelids  and  lashes. 

Tylosis  (ty-lo'-sis).  (Gr.  "knot"  +  suffix  osis  = 
condition.)  A  thickened,  ulcerated  condition  of 
the  lid  margins  after  ulceration. 

Typhlorogy.  (Gr.  typhlos  =  blind  +  logia  =  dis- 
course.)    A  treatise  on  blindness. 

Typlilo'sis.  (Gr.  typhlos  =  blind  +  osis  =  condi- 
tion.)   Blindness. 


U  LCER.  (L.  ulcus.)  An  open  sore,  other  than 
a  wound. 

Ulceration  (ui-ser-a'-shun).  Formation  of  an  ulcer. 

Umbo  (um'-bo).  (L.  prominence.)  The  apex, 
pointed  or  protuberant  part  of  any  substance. 
When  applied  to  lenses,  the  extreme  elevation 
of  a  convex  spherical  lens,  or  it  may  apply  to 
the  center  of  a  concave  spherical  lens. 

Umbra.     (L.  umbra  =  a  shadow.)     A  shadow. 

Undula'tion.  (L.  unda  =  wave.)  A  wave-like  mo- 
tion in  any  medium. 


Un'dulatory  Theory.  A  theory  that  light,  heat 
and  electricity  move  with  a  wave-like  motion. 

Uniaxial  (u-ne-ak'-se-al).  (L.  unus  =  one.)  That 
which  has  but  one  axis. 

Unioc'ular.  (L.  unus  =  one  +  oculus  =  eye.)  Only 
one  eye. 

Unit  (u'-nit).  (L.  unus  =  one.)  Any  standard 
quantity  by  the  representation  and  subdivision 
of  which  any  other  quantity  of  the  same  kind  is 
measured. 

Uremia  (u-re'-me-ah),  (Gr,  "urine"  +  haima  = 
blood.)  Blood  poisoning  from  retained  urinary 
excretions. 

Uvaeformis  (u-ve-for'-mis).  (L.  uva  =  grape -f- 
forma  =  form.)     The  middle  coat  of  the  choroid. 

Uvea.  (L.  uva  ^  grape.)  The  choroid,  ciliary 
body,  and  iris  together. 

Uveal  (u'-ve-al).  That  which  refers  to  the  vascu- 
lar layer  of  the  choroid  coat,  or  the  ciliary  body 
and  iris. 

Uveal  Coat.  The  second  tunic  or  coat  of  the  eye- 
ball. 

Uveitis  (u-ve-i'-tis).  (L.  uva  =  grape -f  itis  =  in- 
flammation.) That  condition  in  which  the  uvea 
is  inflamed.    Iritis. 


V. 


•    Abbreviation  for  vision. 

Vein.     (L.  venio  =  I  proceed.)     The  blood-vessels 

which   convey   blood   toward   the   heart.     They 

are  found  wherever  there  are  arteries.     Veins 

have  three  coats  like  the  arteries,  but  they  are 


OPHTHALMIC  DICTIONARY  260 

not  SO  thick.  The  veins  draining  the  eyeball 
correspond  in  their  arrangement  to  that  of  the 
arteries,  the  main  groups  being  the  retinal, 
anterior  and  posterior  ciliary  veins.  The  venae 
vorticosae,  collects  the  blood  from  the  choroid, 
ciliary  body,  and  the  iris  and  pierces  the 
sclerotic  coat  near  its  equator  as  four  large 
trunks  about  equal  distance  from  one  another, 
where  it  is  joined  by  the  episcleral  veins.  The 
anterior  ciliary  veins  receive  the  blood  from  the 
ciliary  muscle  and  Schlemm's  Canal,  and  after 
emerging  from  the  sclerotic  coat  it  receives  as 
tributaries  the  episcleral  and  vessels  from  the 
conjunctiva.  These  veins  upon  emerging  from 
the  eye  unite  with  the  other  veins  from  mus- 
cles and  tissue  to  form  two  main  trunks,  the 
superior  and  inferior  ophthalmic,  which  run 
along  the  roof  and  floor  of  orbit  to  terminate 
in  the  cavernous  sinus.  The  ophthalmic  vein 
joins  the  internal  angular  vein  (facial)  at  the 
inner  and  outer  angle  of  the  orbit,  thus  escaping 
from  the  orbit  in  either  direction.  The  inferior 
ophthalmia  vein  arises  in  the  veins  of  the  eye- 
lids and  lacrimal  sac,  it  also  receives  the  veins 
from  the  floor  of  the  orbit  and  passes  out 
through  the  sphenoidal  fissure. 

Velocity.  (L.  velocitas,  from  velox  =  swift.) 
Quickness  of  motion. 

Venae  Vortico'sae  ("a  whirlpool").  The  veins 
which  principally  form  the  external  or  venous 
layer  of  the  choroid  coat  (second  tunic)  of  the 
eye;  so  called  from  their  peculiar  arrangement, 
four  of  them  passing  out  about  halfway  back. 

Ventricle  (ven'-tri-kl).  A  small  belly-like  cavity, 
as   the  two   inferior   cavities   of  the  heart   and 


various  cavities  in  the  brain,  of  which  there  are 
five  in  number,  namely,  the  two  lateral,  the 
third,  fourth  and  fifth.  The  lateral  ventricles 
are  the  cavities  of  each  half  of  the  cerebrum. 
The  third  ventricle  is  between  the  optic  thalami 
at  the  base  of  the  brain.  The  fourth  V.  is  the 
space  between  the  cerebellum  and  the  medulla 
oblongata.     Fifth  V.  is  in  the  septum  lucidum. 

Vertex  (ver-teks).  (L.  vertex  =  top  from  vertere 
=  to  turn.)  A  turning  point;  the  principal  or 
highest  point;  top;  summit.  The  point  in  any 
figure  opposite  to,  and  farthest  from,  the 
base;  the  terminating  point  of  some  particular 
line  or  lines  in  a  figure  or  a  curve:  vertex  of 
a  curve  is  the  point  in  which  the  axis  of  the 
curve  intersects  it.  Vertex  of  an  angle  is  the 
point  in  which  the  sides  of  the  angle  meet. 
A^'ertex  of  a  solid  or  of  a  surface  of  revolution 
is  the  point  in  which  the  axis  pierces  the 
surface. 

Vertical.  Situated  at  the  vertex  or  highest  point. 
Vertical  line  is  a  line  perpendicular  to  the  hori- 
zon. Vertical  plane.  A  plane  passing  through 
the  vertex  of  a  cone,  and  through  its  axis.  (See 
Vertex.) 

Virtual  Focus.  (L.  virtus  —  power  +  "the  hearth.") 
An  imaginary  or  negative  focus. 

Visibility  (vis-i-bil'-i-ty).  That  which  has  the  ca- 
pacity of  being  seen. 

Vision.  (L.  videre  =  to  see.)  The  ability  of  the 
organ  of  sight  (the  eye)  to  recognize  surround- 
ing objects.  Double  v.,  see  Diplopia.  Binocular 
v.,  seeing  an  object  with  both  eyes  at  the  same 


OPHTHALMIC  DICTIONARY  271 

time  without  diplopia.     Monocular  v.,  the  act  ot 
seeing  with  only  one  eye. 

Visual.  Pertaining  to  vision  or  sight.  V.  Angle, 
an  angle  formed  by  lines  drawn  from  the  ex- 
treme edges  of  an  object  which  cross  at  the 
nodal  point.  V.  Axis,  a  line  drawn  from  the 
macula  lutea  through  the  nodal  point  to  the  ob- 
ject looked  at.  V.  Field,  the  space  containing 
all  objects  visible  while  the  eye  is  in  a  fixed 
position.  V.  Purple,  purple  pigment  to  be  found 
in  the  retina,  which  is  bleached  by  the  action 
of  light. 

Visual  Acuteness.  The  amount  seen  by  the  naked 
eye  if  emmetropic;  if  ametropic,  while  wearing 
his  correction.  The  smaller  the  objects  that 
the  eye  can  distinguish,  or  the  greater  the  dis- 
tance at  which  an  object  of  given  size  can  be 
seen,  the  greater  is  the  acuity  of  vision  the  eye 
possesses. 

Vitreous  (vit'-re-ous).  (L.  vitrum  =  glass.)  A 
transparent  fluid  occupying  the  posterior  and 
interior  four-fifths  of  the  eye. 

Vitreous  Humor.  (L.  vitrum  =  glass  +  humere  = 
to  be  moist.)  A  transparent,  colorless,  gela- 
tinous mass  which  fills  the  posterior  cavity, 
four-fifths  of  the  eye.  It  somewhat  resembles 
the  white  of  an  egg  and  is  surrounded  by  the 
hyaloid  membrane.  See  Anatomy.  Its  index 
of  refraction  is  1.33. 

Volume  (vol'-um).  (L.  volvere  =  to  roll  around.) 
Solid  contents. 

Von  Graefe's  Sign.  That  condition  where  the  lid 
fails  to  move  downward  with  eyeball  in  exoph- 
thalmic goiter. 


w 


ALL-EYE.  This  term  has  several  meanings. 
It  generally  refers  to  white  opacities  of  the  cor- 
nea or  a  pale  blue  iris.  Sometimes  divergent 
strabismus. 

Wave  Theory.     The  theory  that  light  travels  in 
waves  instead  of  rays.     See  Light. 

Wink.    The  act  of  opening  and  closing  the  eyelid 
suddenly. 

Winker.    See  Eyelash. 

Worsted   Test.     The   common   test   employed   for 
color-blindness. 


X 


ANTHELASMA  (zan-thel-as'-mah).  (Gr.  xan- 
thos  =  yellow  +  elasma  ==  a  beaten  metal  plate.) 
That  condition  in  which  there  is  a  flat  tumor  of 
a  dirty  sulphur-yellow  color  which  projects  a 
little  above  the  skin  of  the  lid.  It  is  found 
most  frequently  on  the  upper  and  lower  lids  at 
the  inner  angle  of  the  eye. 

Xanthocyanopla  (zan-tho-cy-an-o'-pi-ah).  (Gr.  xan- 
thos  =  yellow  +  kyanos  =  blue  +  ops  =  eye.) 
That  condition  in  which  there  is  an  inability  to 
perceive  red  and  green  colors. 

Xanthoma  (zan-tho'-mah).  (Gr.  xanthos  =  yellow.) 
A  yellowish  new  growth  on  the  skin. 

Xanthophane.  (Gr.  xanthos  =  yellow.)  A  condi- 
tion in  which  objects  appear  yellow. 

Xeroma  (ze-ro'-mah).  (Gr.  xeroa  =  dry.)  That 
condition  where  the  conjunctiva  is  abnormally 
dry. 


<  il'JIIllAL.MH'    DK'IIONAKV  2T.'. 

Xerophthalmia  ( zo-rof-thar-nii-ah  ).  (CIr.  xeros — 
dry  +  ophthalmos  ^-  eye.)  Conjunctivitis  with 
atrophy  and  no  liquid  discharge. 

Xerosis  (ze-ro'-sis).     (Or.  xeros  =  dry.)   Abnormal 

dryness  of  the  eye. 


1  ELLOW  SPOT.  The  macula  lutea. 
Young-Helmholtz  Theory  of  Color  Blindness. 
rrhoniiis  Young,  English  physicist,  1773-lS:ii>; 
Herman  Ludwig  Helmholtz,  German  physicist. 
1821-1894.)  The  theory  that  color  vision  de- 
pends on  three  sets  of  retinal  fibers  which  cor- 
respond to  the  colors  red.  violet  and  green. 


#jEISS"S  GLANDS.  The  sebaceous  or  sweat 
i; lauds  locaird  al  the  free  border  of  the  eyelids. 

Zinn's  Ligament.  (Johann  Gottfried  Zinn,  German 
anatomist,  1727-1759.)  A  circular  ligament  at 
the  optic  foramen  from  which  arises  the  recti 
muscles  of  the  eye;  the  ligament  itself  is  at- 
tached to  the  bone  and  allows  the  optic  nerve 
to  pass  through  its  center. 

Zone.     (L.  girdle.)     A  girdle  or  belt. 

Zonula.  A  very  small  membrane  surrounding  a 
body.    A  small  zone. 

Zonule  of  Zinn.  The  suspensory  ligaments  of  the 
t^ye-lens  form  the  Zone  of  Zinn.  It  consists  of 
delicate  fibers  which  take  their  origin  from  the 
inner  surface  of  the  ciliary  body,  beginning  at 
the  ora  serrata.  The  fibers  are  in  contact  with 
the  surface  of  the  ciliary  body,  but  leave  it  at 


the  apices  of  the  ciliary  processes,  and,  becom- 
ing free,  divide  and  pass  over  to  the  edge  of  the 
lens,  thus  forming  the  anterior  and  posterior 
suspensory  ligaments.  These  ligaments  are  at- 
tached to  the  capsule  of  the  lens  with  which 
they  become  fused.  The  space,  triangular  in 
shape,  included  between  the  fibers  of  the  zonule 
or  suspensory  ligaments  and  the  edge  of  the 
lens  is  called  the  Canal  of  Petit. 

Just  outside  of  the  optic  nerve,  where  it 
pierces  the  eyeball,  is  found  a  circle  of  blood- 
vessels giving  a  free  supply  to  the  optic  sheath 
at  this  point,  and  sending  branches  into  the 
substance  of  the  nerve  to  supply  nutrition.  This 
circle  is  known  as  the  Circulus  of  Zinn  or  some- 
times called  a  Zone  of  Zinn. 
Zonulitis.  (L.  zonula  +  Gr.  itis.)  Inflammation 
of  the  zonule  of  Zinn. 


OPHTHALMIC  DICTIONARY  275 

A    FEW    QUESTIONS    WITH    THEIR    ANSWERS 

1.  Q.  What  governs  the  passage  of  light  through 

any  transparent  media? 
A.  Density. 

2.  Q.  On  what  does  the  visual  angle  depend  for 

its  existence? 
A.  The  size  and  distance  of  the  object. 

3.  Q.  What  three  laws  accompany  refraction? 
A.  Reflection,  absorption  and  dispersion. 

4.  Q.  In  what  three  ways  can  an  incident  ray  be 

disposed  of? 
A.  Reflected,  absorbed  or  refracted. 

5.  Q.  What  three  laws  must  be  brought  into  play 

in  order  to  obtain  distinct  binocular  vision 
at  various  distances? 
A.  Refraction,    accommodation    and    converg- 
ence. 

6.  Q.  Why  is  it  necessary  for  the  aqueous  humor 

to  be  thinner  than  the  vitreous  humor  and 
yet  have  the  same  density? 
A.  To  allow  freedom  of  movement  to  the  iris. 

7.  Q.  Why  is  accommodation  and  convergence  so 

closely  associated? 
A.  Because    they    are    both    operated   by   the 
same  nerve. 

8.  Q.  What  lens  represents  the  focal  strength  of 

the  dioptric  system  of  the  eye? 
A.  From  62  to  65-D.  plus. 

9.  Q.    vVhen  is  a  lens  periscopic? 

A.  When  it  is  minus  on  one  side  and  plus  on 
the  other. 
10.  Q.  What   are   objective  and   subjective   symp- 
toms? 

A.  Objective  symptoms  are  what  the  operator 
detects    without    questioning    the    patient. 


Subjective   symptoms   are   those   described 
by  the  patient. 

11.  Q.  Why  does  Astigmatism   in  one   eye  some- 

times cause  convergent  Strabismus? 
A,  In    order    to    prevent    the    eye    Avith    the 
blurred  vision   interfering  with   the  vision 
of  tlie  good  eye  the  patient  learns  to  turn 
it  toward  the  nose. 

12.  Q.  Why  do  we  add  and  subtract  from  retino- 

scopic  findings? 
A.  To  place  the  patient's  far  point  at  20  feet. 

13.  Q.  Why   is   the   concave   retinoscope   superior 

to  the  plane? 
A.  Because   a   concave   retinoscope   combined 
with  a  plus  20-D.  lens  can  be  used  as  an 
ophthalmoscope. 

14.  Q.  What   lens   can   be   combined   with    plus    2 

sphere  combined  with  plus  1  cylinder,  axis 
90,  that  will  increase  the  cylinder  and  de- 
crease the  sphere? 
A.  Any  minus  cylinder  under  2  dioptrics  with 
its  axis  at  180. 

15.  Q.  What  is  false  myopia,  and  how  is   it   pro- 

duced? 
A.  A  spasm  of  accommodation  in  emmetropia 

will  cause  the  eye  to  appear  myopic,  and  is 

brought  about  by  continual  strain  at  close 

work,  exophoria  or  hyperopia. 
Ifi.  Q.  Is    an    Ophthalmic    lens    used    to    improve 

vision? 
A.  No.     The  lens  is  to  refract  the  light  only, 

which   sometimes  brings  the   focus   nearer 

to  the  retina  resulting  in  better  vision. 
17.  Q.  Could    Strabismus    exist    and    <he    eyes    be 

Orthophoric? 


OPHTHALMIC  DICTIONARY  277 

A.  Yes.  The  deviation  may  be  due  to  Hyper- 
metropia  or  abnormal  vision  in  one  eye 
only. 

18.  Q.  Can  an  eye  be  parallel  with  its  fellow  while 

wearing  a  single  prism? 
A.  Not  unless  the  Macula  Lutea  is  displaced. 

19.  Q.  Do   prisms  make  eyes   parallel  in   Hetero- 

phoria? 
A.  No.      They    allow    them    to    deviate    from 
parallelism. 

20.  Q.  Name    three    things    that    would    interfere 

with  the  action  of  accommodation. 
A.  Paralysis,   hardening   of   the   lens,   loss   of 
Crystalline  Lens. 

21.  Q.  What    three    things    determine    the    focal 

length  of  a  lens? 
A.  Curvature,  density  and  distance  of  object. 

22.  Q.  What  is  a  prism  diopter? 

A.  The  power  of  a  prism  to  deviate  a  ray  of 
light  one  centimeter  in  a  meter. 

23.  Q.  What  are  the  constituents  of  Crown  Glass? 
A.  Crown   glass   is   so   called   from   the   trade- 
mark  by   the    early    manufacturers.      It    is 
composed  of  lime,  sand  and  soda. 

24.  Q.  What  is  the  composition  of  Flint  Glass? 

,  A.  Somewhat  like   Crown  only  less   sand  and 
lead  is  used  to  increase  its  density. 

25.  Q.  Which  is  the  harder,  flint  or  crown  glass? 
A.  Crown   glass  is  about  20   per  cent  harder^ 

because  it  has  no  lead  and  more  sand. 

26.  Q.  Which  has  the  most  dispersive  power,  flint 

or  crown? 
A.  Flint   has   the   most   dispersive    power,   be- 
cause of  its  higher  index  of  refraction. 


278  LEW'IS  POCKET 

27.  Q.  Transpose  the  following  Rx.: 

—  1.  cyl.  ax.  20 
—2.  sph.+2.50  cyl.  ax.  180 
4-  .50  sph.  +  l  cyl.  ax.  60 
A.  —  1  spli.  -f  1  cyl.  ax.  110 
+.50  sph.  — 2.50  cyl.  ax.  90 
—  1.50  sph.  —  1  cyl. ax. 150 

28.  Q.  TMiat  errors   of  refraction   will   the   above 

prescriptions  correct? 
A.   (a)   Simple  myopic  astigmatism,    (b)  Mixed 
astigmatism,     (c)  Compound  hypermetropic. 

29.  Q.  What  vision   does   an   emmetropic   eye   al- 

ways have? 
A.  Emmetropia  has  no  reference  whatever  to 
vision,  but  we  expect  normal. 

30.  Q.  Does  a  hypermetropic  eye  ever  have  nor- 

mal vision? 
A.  Yes.    Provided  he  is  able  to  overcome  his 
error  by  accommodating. 

31.  Q.  Name  four  reasons  why  vision  would  not  be 

normal? 
A.  Cataract.   Focus  off  the  retina.    Amblyopia. 
Lucoma. 

32.  Q.  If  an  object  is  80  inches  from  a  -f  3  sphere 

where   will   the   image   be? 
A.  16  inches. 

33.  Q.  If  an  eye  looking  20  feet  away  sees  as  well 

without  as  with  a  +2  sph.  should  it  be  worn? 
Give  reason  for  your  answer. 
A.  Yes.     It    shows    relaxation    from   accommo- 
dation. 

34.  Q.  In  correcting  astigmatism  where  would  you 

place  the  axis  of  the  cylinder,  if  the  spoke 
from  11  to  5  was  seen  the  blackest? 
A.  150  degrees. 


:>J»    Q    WhAi  orrv^r  of  ivtYaction  wouKI  vou  c-^uso 

And  \vouK1  it  bo  with  or  ajiainsst  tho  rulo  if 

you  plaoi?d  a  -f  1  Ql-  a^   lJ^<^  K>foro  an  onv 

motropiv-*  ove? 

A    iNinipIo  Myopio  a^tiiimatisim.    With  tho  ruU\ 

;>ti.  Q    rvv>n    what    i:^    tho    doviatin>:    innver   vM'   a 
V^rism  dopondont  ? 
A.  The  pv^wor  of  pri;?m  is  doptnidont  upon  its 
«ui|rlo  and  its  indox  of  ivtYaotion. 

*^T,  Q   What  is  a  ov>mpvnim1  lens? 

A,  A  Ions  made  with  a  spherical  and  cylin- 
drioal  effoot,  also  known  as  a  sv^heiwoyl^ 
indor 

C>S,  Q    What   IS  tho  kind  of  iilass  tYoni  which  or- 
dinary   spootaolo  lenses   are   madet    What 
is  its  index  t 
A,  It  is  Crown  Glass      Index  varies  t>i"»m  1  50 
to  1  5:V 

Si*,  Q    What  does  myosis  with  photophobia  in  nor- 
mal lij:ht  indicate t 
A,  Myosis   in   normal    lijtht    with    photophobia 
indicates  a  serious  disease,  as  a  nile. 

40,  Q   What  is  the  first  thiiv.^  to  do  in  making  an 
examination? 
A    >Cxamine  for  diseased  conditions  befortMVir- 
rectins  errors  of  refraction. 

41  0  How  would  you  prove  a  pair  of  eyes  has 
cxophoria  that  roiiuin^s  a  prismatic  correc- 
tion for  constant  wear* 
A,  If  after  the  patient  has  worn  his  distjtnt 
correctio>n  for  the  ametrt^pia  a  few  weeks 
the  muscle  trouble  remains,  1  would  tvciire 
to  correct  the  trouble  With  the  maddox 
Tv»d  horizontal  before  the  ri»;ht  eye  and  the 
rt>d  glass  befort^  the  left,  the  jvitient   will 


280  LEWIS  POCKET 


see  the  red  light  to  the  right  of  streak,  and 
it  would  require  prisms  base  in  to  bring 
them  together,  proving  exophoria. 


Points  one  should  be  familiar  with  before  attempt- 
ing a  State  Examination: 

1.  Mechanical  parts  of  frames  and  guards  for 
mounting  lenses;  making  face  measurements 
for  same;  truing  up  bent  frames  and  guards; 
adjusting  same  to  different  persons. 

2.  The  common  shapes  and  forms  and  diop- 
tric values  of  lenses  of  different  kinds;  sub- 
mitting ten  different  kinds  to  applicants  for 
determination  of  these  qualities. 

3.  Practical  fitting  with  trial  case,  a  test  of 
the  applicant's  practical  ability  to  go  through 
these  tests  and  accurately  fit  different  classes 
of  cases  with  lenses. 

4.  Shadow  testing,  with  or  without  stand  in- 
strument; the  actual  doing  of  this  work  and 
determining  the  error  of  refraction  by  the 
method.  The  mirror  or  instrument  preferred 
may  be  used, 

5.  Muscle  testing,  and  the  use  of  muscle  test- 
ing devices;  a  test  of  the  applicant's  ability  to 
make  these  tests  and  draw  correct  conclusions 
from   them   and   their   showings. 

6.  The  proper  use  of  different  optical  instru- 
ments used  to  measure  the  refraction  of  the 
eyes  or  any  surface,  or  the  power  of  the  mus- 
cles of  the  eyes. 

7.  Questions  on  the  anatomy  and  physiology 
of  the  eyes,  including  muscles,  nerves,  tissues 
and  their  functions. 

8.  Questions  on  retraction  of  lenses,  transpo- 
sition, conjugate  foci,  image  forming,  and  the 
media  of  the  eye. 


OPHTHALMIC  DICTIONARY  281 

GROUP  ONE. 

1.  Name  the  extrinsic  and  intrinsic  muscles  of 
the  eye. 

2.  Describe  the  Iris,  the  muscles  that  control  its 
movements  and  the  mechanism  that  causes  the 
pupil  to  contract  and  expand,  what  causes  the 
movements  and  how  they  assist  in  procuring  clear 
vision. 

3.  Describe  the  humors  of  the  eye  and  why  it  is 
desirable  that  a  certain  humor  be  more  fluid  than 
the  others. 

4.  Describe  the  Choroid  and  its  functions. 

5.  Describe  the  Crystallme  Lens.  What  holds 
it  in  position?  What  controls  and  alters  its  sh^pe? 
What  is  its  index  of  refraction?  What  is  its 
strength  in  diopters  and  how  does  it  assist  in 
procuring  good  vision? 

6.  Describe  the  Optic  Nerve  and  Retina  and 
their  functions. 

7.  Is  the  human  eye  chromatic  or  achromatic? 
How  can  it  be  proven? 

8.  Describe  the  Conjunctiva  and  its  office. 

9.  Which  part  of  the  eye  has  the  greatest  re- 
fracting power?    Why? 

10.  Describe  the  eyelids,  eyebrows,  eyelashes 
and  the  office  of  each. 

11.  Describe  the  Lachrymal  Gland  and  its  ap- 
pendages and  their  office, 

12.  In  which  part  of  the  brain  are  the  optic  cen- 
ters situated? 

13.  Describe  the  principal  veins  and  arteries  of 
the  eye. 

14.  Prom  what  source  does  the  Cornea  receive 
its  supply  of  nourishment? 

15.  What  is  meant  by  abduction?     Adduction? 


282  LEWIS  POCKET 

Sursumduction?  Torsion?    Name  the  muscles  that 
produce  them. 

16.  Define  visual  angle;  minimum  visual  angle; 
visual  acuity. 

17.  What  is  Pterygium?  Trachoma?  Nystag- 
mus?   Keratitis? 

18.  Explain  the  Helmholts  and  Tscherning  the- 
ories of  accommodation.  Which,  in  your  opinion, 
is  more  reasonable?    Why? 

19.  What  do  you  understand  by  Co-ordinate 
movements  of  the  eye? 

20.  Make  a  diagram  of  an  eye,  showing  the 
principal  parts,  briefly  describing  the  functions  of 
eaoh  part. 

GROUP  TWO. 

1.  Explain  what  is  meant  by  the  Conjugace 
movements  of  the  eyes. 

2.  What  is  the  retractive  condition  and  ampli- 
tude of  accommodation  of  a  person  whose  P.  R. 
with  a  plus  5  D.  Sphere  is  50  C.  M.  and  whose 
P.  P.  with  a  plus  2  D.  Sphere  is  10  C.  M.? 

3.  What  is  the  usual  size  of  the  ocular  pupil  in 
uncorrected  ametropes  who  do  not  complain  of 
asthenopia? 

4.  A  person  has  a  fixed  deviation  outward  of 
one  eye  of  4  meter  angles.  What  prism  will  cause 
the  images  to  fuse  at  50  C.  M.?  Where  would  you 
place  the  base  of  the  prism? 

5.  Describe  fully  your  method  of  measuring  the 
relative  strength  of  the  extrinsic  muscles  of  the 
eyes. 

6.  Give  the  rule  for  the  prism  diopral  decentra- 
tion  of  lenses,  and  work  the  following  problem  by 
it:  A  pair  of  plus  3  D.  S.  are  decentered  5  mm. 
inward.    How  much  prism  value  results? 


OPHTHALMIC  DICTIONARY  283 

7.  Give  the  rule   for  transposing  plus  spheres 
I    combined  with  plus  Cyl's  to  plus  Sph.  combined 

with  minus  Cyl's  and  work  the  following  by  it 
(leaving  your  figures  on  the  paper):  (a)  Plus  1.75 
D.  S.  combined  with  plus  .75  D.  C,  axis  15.  (b)  Plus 
1.25  D.  S.  combined  with  plus  1.50  D.  Cyl.  axis  135. 

8.  Give  the  rule  for  transposing  cross  Cyl's  into 
Sphero  Cyl,  and  work  the  following  by  it,  leaving 
your  figures:  (a)  Plus  1  D.  C.  axis  90  combined 
with  a  plus  2  D.  C.  axis  180.  (b)  Plus  1.25  D.  C. 
axis  90  combined  with  a  minus  .50  D.  C.  axis  180. 

9.  In  Retinoscopy  what  is  the  nature  of  the 
refraction  of  the  eye  under  observation  when  one 
point  of  reversal  is  found  at  20  inches  and  another 
at  40  inches? 

10.  A  coin  one  inch  in  diameter  is  held  12  inches 
from  a  lens,  the  principal  focus  of  which  is  4 
inches.    Where  will  the  image  be  formed? 

11.  Explain  the  relation  existing  between  accom- 
modation and  convergence. 

12.  Explain  the  principles  governing  the  use  of 
the  Ophthalmometer  and  its  practical  working. 
To  what  extent  can  it  be  relied  upon  as  a  means 
of  estimating  refractive  errors? 

13.  A  child  of  10  years  who  has  never  worn 
glasses  is  found  to  have  4  D.  of  hyperopia  and 
esophoria  of  5  degrees.  Would  you  order  prisms 
or  decenter  the  lenses  in  this  case? 

14.  A  certain  prescription  reads  plus  1  D.  S. 
combined  with  plus  1.25  D.  C.  axis  90.  Give  the 
dioptric  value  of  the  surfaces  of  the  lens. 

15.  Define  Anisometropia;  Asthenopia;  Amblyo- 
pia; Orthophoria. 

16.  With  the  static  method  and  the  retinoscope 
at  40  inches  the  shadow  is  neutral  with  a  plus  Z 


284  LEWIS  POCKET 

Sphere  before  the  observed  eye.    What  two  points 
are  conjugate  and  what  is  correction  for  that  eye? 

17.  In  static  skiametry  with  plane  mirror  at  26 
inches  and  a  plus  1.50  D.  S.  in  rear  cell  of  trial 
frame  no  movement  is  found  in  the  horizontal 
meridian  and  a  plus  .75  Sph.  neutralizes  motion 
in  the  vertical  meridian.  What  direction  had  the 
shadow  before  the  plus  .75  D.  S.  was  used?  What 
kind  and  amount  of  ametropia  was  indicated? 

18.  A  boy  of  14  years  has  vision  equal  to  20-15 
without  glasses.  Would  you  accept  that  as  proof 
of  emmetropia?    Give  your  reasons. 

19.  If  double  concave  lens  could  be  made  of  air 
with  its  radius  of  curvature  20  inches  for  each 
side,  what  would  be  the  nature  of  its  refraction  if 
it  were  immersed  in  water  and  what  would  be  its 
action  on  parallel  rays  of  light? 

20.  If  a  person  15  years  of  age  should  come  to 
you  to  have  a  complete  examination  of  the  eyes, 
how  would  you  proceed?  What  questions  would 
you  ask  and  how  would  you  proceed  to  make  the 
examination,  together  with  the  record  you  would 
make?  Give  full  particulars  just  as  if  you  had 
such  a  case. 

GROUP  THREE. 

1.  What  is  light?  How  does  it  travel  from  a 
luminous  pomt?  What  three  things  may  happen 
to  it  when  it  comes  in  contact  with  another 
medium? 

2.  What  is  reflection?  Give  the  law  governing 
incident  and  reflected  rays.  If  a  ray  is  incident 
at  an  angle  of  30  degrees,  at  what  angle  will  it  be 
reflected? 

3.  The  radius  of  curvature  of  a  concave  mirror 
is  16  inches.     What  will  be   its  principal  focus? 


OPHTHALMIC  DICTIONARY  >:> 

If  a   candle  is  placed  12  inches  in  front   of  it,  at 
what  distance  will  its  image  be  formed? 

4.  What  is  refraction?  Make  a  diagram  sliow- 
ing  the  path  of  a  ray  of  light  as  it  strikes  the 
surface  of  a  plate  of  glass,  as  it  passes  through. 
and  after  it  emerges.  What  are  the  three  parts 
of  the  ray  called? 

5.  What  is  meant  by  the  term  "surface  power 
of  a  lens"?  A  certain  lens  has  a  surface  power  of 
plus  6.25  D.  S.  on  one  side  and  on  the  other  minus 
1.25  D.  S.  What  curvatures  must  a  cement  seg- 
ment have  to  make  the  reading  portion  plus  6  D. 
when  the  index  of  refraction  is  the  same  in  both 
parts  of  the  lens? 

6.  Make  diagram  showing  three  double  convex 
lenses  and,  the  course  of  parallel  rays  of  light 
through  them,  the  principal  focus,  the  secondary 
focus,  and  one  pair  of  conjugate  foci. 

7.  A  plus  2.50  D.  S.  is  held  30  inches  from  a 
candle.     Where  will   the   image   be  formed? 

8.  The  light  from  a  candle  passes  through  a 
plus  3  D.  S.  at  50  C.  M.  Where  should  a  screen 
be  placed  to  get  the  best  defined  image?  Show 
your  method  of  working  this  problem. 

9.  A  certain  lens  focuses  parallel  rays  of  light 
at  20  C.  M.  What  lens  must  be  placed  in  front  of 
it  t©  send  the  focus  back  to  one  meter? 

10.  What  is  meant  by  "the  power  of  a  prism"? 
If  you  had  two  weak  prisms  and  desired  to  know 
their  powers  within  one  per  cent,  what  method 
would  you  (Miiploy  and  how  would  you  proceed  to 
carry  out  the  measurement? 

11.  Describe  how  bifocal  lenses  should  be  ad- 
justed and  the  position  which  the  reading  portion 
should  occupy. 


2S6  LEWIS    POCKET 

12.  A  plus  1.50  D.  piano  Cyl  is  placed  in  contact 
with  a  similar  one  of  plus  .75  D.;  axis  right  angles. 
What  Is  the  resultant  combination? 

13.  If  you  desired  to  find  the  power  of  a  double 
concave  lens  and  had  no  lens  measure  or  neutral- 
izing lenses,  how  would  you  proceed  if  the  index 
of  refraction  of  the  glass  was  1.50? 

14.  Give  the  rule  for  transposing  plus  spheres 
combined  with  minus  Cyls  and  work  the  following 
by  it:  Plus  3  D.  S.  combined  with  minus  1.25 
D.  C.  axis  45.  Plus  2  D.  S.  combined  with  minus 
2.50  D.  C.  axis  65. 

15.  Transpose  the  following: 

Plus  3.50  D.  S.  plus  1.25  D.  C.  axis  135. 
Plus  2  D.  S.  plus  D.  C.  axis  65. 
Minus  3  D.  C.  minus  2  D.  C.  axis  75. 
Minus  2  D.  S.  minus  3.25  D.  C.  axis  155. 
Plus  2.25  D.  C.  axis  90  plus  150  D.  C.  axis  180. 
Minus  2.25  D.  S.  plus  175  D.  C.  axis  135. 

16.  What  error  will  the  following  prescription 
correct:  R.  plus  1  D.  S.  minus  .75  D.  C.  axis  180, 
combined  with  2  degree  prism  base  up. 

17.  Describe  Glaucoma.  Trachoma,  Pterygium. 
Cataract.    Granulated  lids. 

18.  What  is  Ophthalmia  Neonatorum?  What 
simple  method  will  prevent  it? 

19.  Describe  the  fogging  method  of  measuring 
refraction  and  your  everyday  manner  of  apply- 
ing it. 

20.  A  young  person  complains  of  Asthenopia 
and  the  third  trial  case  shows  Myopia  of  1.25  D. 
The  Retinoscope  shows  1.50  of  Hyperopia.  What 
would  you  give  in  the  way  of  lenses?  Why  would 
you  give  them? 


MEMORANDUM 


MEMORANDUM 


-I 


14  DAY  USE 

"r'^N  TO  DFSK  FROM  WHICH  >^nRRow.;D 


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U.C.  BERKELEY  LIBRAr 


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